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  • American Institute of Physics (AIP)  (241,959)
  • Periodicals Archive Online (PAO)  (190,459)
  • International Union of Crystallography (IUCr)
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  • 101
    Electronic Resource
    Electronic Resource
    Determining the lattice relaxation in semiconductor layer systems by x-ray diffraction (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 3121-3125 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This paper illustrates the procedure for extracting structural information available from x-ray diffraction space mapping and topography. The methods of measuring, the residual strain, macroscopic tilts, microscopic tilts and their lateral dimensions, and the strain field disruption emanating from the interfacial defects are presented. Partially relaxed thick InGaAs layers on GaAs substrates were studied and it was concluded that the relaxation and macroscopic tilting were anisotropic, the microscopic tilting reduced with thickness, and the interfacial disruption did not continue to increase with increasing relaxation. A "mosaic grain growth'' model is postulated to account for the diminishing microscopic tilt spread and increasing topographic contrast with layer thickness.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354578
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  • 102
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    X-ray induced modification of metal/fluoropolymer interfaces (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1744-1746 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Metal adhesion to polymers depends on the chemical structure at the interface. In the present work, we study the evaporation of Cr, Ti, and Au onto Teflon PFA (perfluoromethyl-vinyl-ether) substrates, and we modify the interface by post-deposition x-ray irradiation. In situ x-ray photoelectron spectroscopy shows that deposition of reactive metals such as Cr and Ti leads immediately to crosslinking and to the formation of carbide and fluoride species. Less reactive metals, such as Au, cause only small loss of fluorine without formation of any new species. The metal/PFA interface is strongly affected by x-ray irradiation in the case of Cr and Ti: remarkably enhanced crosslinking has been observed, which further increases with the metal coverage, while the carbides and fluorides remain basically unaffected. On the other hand, crosslinking increases only very slightly for pure PFA and for the Au/PFA interface, regardless of the Au thickness. These results suggest that radical recombination reactions are responsible for crosslinking at the interface between PFA and reactive metals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354803
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  • 103
    Electronic Resource
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    Parameter fitting in grazing incidence x-ray reflectometry (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1776-1780 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A method for parameter identification in grazing incidence x-ray reflectometry is presented. It is based on a nonlinear least-squares approach with on-line low-pass filtering and fits the measured reflectivity curve as a function of the incidence angle to a simulation model. The filter is applied in the (angular) frequency domain; it introduces, even for strong filtering, no bias and renders the result independent of the angular stepsize of the data. Automatic restarting helps to determine the global solution. The commonly used roughness model is generalized to non-normal distributions in order to assess data with large scattering vectors. The method is demonstrated for data from single and double film samples. Thickness and roughness can be determined with an accuracy of about 0.2 nm. However, only in special cases it is possible to determine accurately materials constants such as compositional fractions or densities. Absorption cannot be neglected, but the corresponding parameters are difficult to determine separately.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354807
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  • 104
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    Segregation and interdiffusion of In atoms in GaAs/InAs/GaAs heterostructures (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1770-1775 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The segregation and interdiffusion of In atoms in the GaAs/InAs/GaAs heterostructures were investigated by secondary-ion mass spectroscopy. When the 1-ML-thick InAs layer was grown in a layer-by-layer growth mode with no dislocations, the segregation of In atoms became marked with the increase of the growth temperature. However, the segregation was observed even at a relatively low growth temperature of 400 °C in molecular beam epitaxy. It was found that the segregation was markedly enhanced by dislocations near the heterointerface when thick InAs layers were grown in a three-dimensional island growth mode. The interdiffusion of In atoms toward the growth direction occurred after thermal annealing, which could be assisted by vacancies propagating from the film surface into the epilayer. It became apparent that the interdiffusion was effectively suppressed by a thin AlAs layer inserted in the GaAs cap layer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354806
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  • 105
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    Monte Carlo simulation of electron transport in gallium nitride (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1818-1821 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The results of an ensemble Monte Carlo simulation of the electron transport in gallium nitride (GaN) are presented. The calculation shows that intervalley electron transfer plays a dominant role in GaN in high electric fields leading to a strongly inverted electron distribution and to a large negative differential conductance. An analytic expression for the polar optical momentum relaxation time for phonon energies larger than the thermal energy is also derived. This expression applies to many wide-gap semiconductors, such as GaN and SiC, at room temperature since these semiconductors have large polar optical-phonon energies (on the order of 100 meV). The calculated mobility agrees well with the results of the Monte Carlo calculation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354787
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  • 106
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    Dependence of valence-subband structures on the substrate orientation in ZnSxSe1−x/ZnyMg1−ySzSe1−z quantum wells (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1822-1825 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a theoretical investigation of the growth orientation dependence of valence-subband structures in ZnSxSe1−x/ZnyMg1−ySzSe1−z quantum wells grown in the [001], [115], [113], [112], and [111] directions. The results indicate that the in-plane effective mass of the heavy-hole subband in the [111]-oriented structure is substantially smaller than that in the [001] quantum wells. For applications to quantum-well lasers, the lighter effective mass will lead to a smaller threshold current density, and therefore a better laser performance. Our investigations should provide useful guidelines for the design of II-VI quantum-well blue lasers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354788
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  • 107
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    Electrical properties of silicon under nonuniform stress (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1832-1837 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a detailed analysis of the electronic carrier transport in silicon when subject to a nonuniform stress distribution. Such a distribution gives rise to two independent current components which can be viewed in terms of carrier generation-recombination. One component arises as a result of the nonuniform stress induced position dependent density of states, and the other due to stress induced shifts in the band edges. The various parameters and coefficients describing these phenomena are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354790
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  • 108
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    Alloy composition dependence of defect energy levels in GaxIn1−xP/InP:Fe and GaxIn1−xP/InP:S (x≤0.24) (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1862-1867 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The defect energy levels in metalorganic chemical vapor deposition (MOCVD) grown GaxIn1−xP/InP:Fe and GaxIn1−xP/InP:S epilayers (x≤0.24) have been studied by photoluminescence (PL) and photoconductivity (PC) measurements. To understand the origin of the observed deep levels, we have determined the temperature dependence of the intensity and half-width of the dominant deep-level PL peaks. We find that (1) the dominant deep-level peaks of the samples grown on the same substrate are related to the epilayer composition, and move to higher energies with increasing gallium content; (2) the dominant deep-level peaks of the samples with the same epilayer composition grown on different substrates are different. They are attributed to the impurity in the substrate diffusing into the epilayer during MOCVD growth, forming an impurity-vacancy complex. The following tentative assignments are proposed: the dominant deep-level peaks in GaxIn1−xP/InP:Fe and GaxIn1−xP/InP:S are attributed to the emission of a (V)P-(Fe)III complex and a (V)III-(S)P complex, respectively. Comparing the deep level with the near-band-edge emission we show that (1) all deep levels are independent of the band edge as x is varied; (2) the composition dependences of the deep levels associated with such complexes depend on the site occupied by the impurity atom.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354794
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  • 109
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    Ambipolar diffusion and carrier lifetime measurements in all-binary (InAs)2(GaAs)5 strained quantum wells grown on GaAs (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1868-1873 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The in-well ambipolar diffusion coefficients and carrier lifetimes in ordered all-binary quantum wells, composed of (InAs)2(GaAs)5 short-period strained-layer superlattices (SPSLSs) grown on [001]-oriented GaAs substrates, are measured using picosecond optically induced transient grating and pump-probe techniques. Quantum wells containing SPSLSs may be expected to exhibit higher in-plane hole mobilities compared to InGaAs ternary alloy quantum wells because of a larger average indium content and reduced disorder scattering in the SPSLS structures. The results obtained in the SPSLSs are compared to those obtained in InGaAs alloy quantum wells of comparable well width and confinement energies. This indicates that, for a given SPSLS and its equivalent alloy, the ambipolar diffusion coefficients are comparable while the carrier lifetimes in the SPSLSs are longer. The longer carrier lifetimes in the SPSLSs suggest that these binary structures possess fewer nonradiative recombination centers than the alloys. The absence of a dramatic improvement in the transport properties, however, may indicate that imperfect interfaces in the SPSLSs may be offsetting their possible advantages, in spite of the fact that optical measurements in the SPSLSs indicate high quality and x-ray and transmission electron microscopic measurements demonstrate the binary nature of these structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355301
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  • 110
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    The determination of valence band discontinuities in Si/Si1−xGex/Si heterojunctions by capacitance-voltage techniques (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1894-1899 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Capacitance-voltage (C-V) profiling has been used to measure the apparent carrier concentration profiles in Si/Si1−xGex/Si structures for a range of Ge percentages. Using Kroemers analysis, good agreement has been found between theoretical valence band offsets and those determined from the experimental data. The validity of Kroemers analysis has been assessed in the presence of traps using a C-V simulation program. Under certain circumstances, large errors occur in the extracted valence band offset due to distortion of the apparent carrier concentration profile by traps. It is proposed that the experimental data presented here falls into a regime where minimal distortion is to be expected and is reflected by the accuracy of the extracted valence band offsets.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354799
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  • 111
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    Epitaxial tetragonal PtCo (001) thin films with perpendicular magnetic anisotropy (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1922-1928 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The ordered PtCo tetragonal intermetallic compound with perpendicular magnetic anisotropy and a preferred c-axis orientation perpendicular to the film plane has been produced by annealing epitaxial multilayers of Pt and Co. These films demonstrate large magnetic anisotropy, magneto-optic Kerr rotations, and magnetization, suggesting them as candidates for magneto-optic and perpendicular magnetic recording.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354775
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  • 112
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    A simulation of the multiple trapping model for continuous time random walk transport (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 3224-3230 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A multiple trapping model is used to study the dispersive transport of holes in insulators. The one-dimensional Poisson and continuity equations are solved numerically along with the trap rate equations that model multiple trapping. The transient current due to a pulse of radiation is obtained as a function of the spread in the trap energy levels and the trap density distribution. The main properties of continuous time random walk transport, namely universality and superlinear dependence of the transit time on the electric field and oxide thickness, are verified.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354596
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  • 113
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    Interband tunneling in nonparabolic semiconductors in the presence of an electric field (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 3246-3250 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An attempt is made to study the interband tunneling rate for small-gap semiconductors having Kane-type energy bands in the presence of an external electric field, taking InSb as an example for the purpose of numerical computations. The experimentally obtained tunneling currents, which may not be limited by the factor 2, can be better explained by this formulation. Thus, the present analysis is applicable for wider ranger of electric fields and are more consistent with the experimental results than that previously proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354599
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  • 114
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    Correlation between Schottky-barrier height and the heat of formation of transition-metal silicides (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 3270-3272 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The intrinsic Schottky-barrier height obtained from an interface-defect-free model has the close correlation with the heat of formation of transition-metal silicides. This linear correlation includes previously anomalous values reported for PtSi and IrSi.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354547
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  • 115
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    A comparison between different numerical methods used to solve Poisson's and Schroedinger's equations in semiconductor heterostructures (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 3273-3276 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A comparison between different numerical methods which are used to solve Poisson's and Schroedinger's equations in semiconductor heterostructures is presented. Considering Schroedinger's equation, both the Rayleigh–Ritz method and the finite difference method are examined. The accuracy and the computational speed are investigated as a function of both the mesh size and the number of Rayleigh–Ritz functions and the numerical results are compared with analytical solutions for special cases. To solve Poisson's equation, direct and iterative methods are implemented and the advantages and limitations of each method are discussed. The previous methods are used to solve Poisson's and Schroedinger's equations self-consistently in typical heterostructures to obtain the wave functions, the carrier distribution, and the subband energies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354548
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  • 116
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    Accurate measurements of the silicon intrinsic carrier density from 78 to 340 K (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 3293-3297 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The intrinsic carrier density in silicon has been measured by a novel technique based on low-frequency capacitance measurements of a p+-i-n+ diode biased in high injection. The major advantage of the method is its insensitivity to uncertainties regarding the exact values of the carrier mobilities, the recombination parameters, and the doping density. The intrinsic carrier density was measured in the temperature range from 78 to 340 K. At 300 K the value of ni was found to be (9.7±0.1)×109 cm−3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354551
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  • 117
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    Characterization of the buried oxide in SOI structures by a rate window method (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 3298-3302 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new method for the characterization of the SOI separation by implanted oxygen (SIMOX) oxide is presented. It is based on the fact that the buried oxide can be polarized by applying a bias in the substrate of the structure. In the process of relaxation, current transients are induced in the Si film, which can be monitored by the rate window technique. The experiment reveals that the relaxation process is thermally activated with one or more time constants. These properties of the SIMOX oxide are attributed to the high metal concentration of the oxide.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354552
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  • 118
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    Stress induced anisotropy and temperature dependence of the magnetostriction in Fe73.5Cu1Nb3Si13.5B9 amorphous alloy (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 3323-3327 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic anisotropy, Kσ, induced by heating under applied tensile stress has been studied for the Fe73.5Cu1Nb3Si13.5B9 amorphous alloy as a function of the annealing temperature. The induction process was carried out by means of current annealing in samples as-quenched and preannealed (TP.A.=400 °C during 2 min). It is found that the easy axis of this anisotropy is transverse to the tensile stress. The dependence of the stress induced anisotropy on annealing temperature is, in both cases, similar to that reported in other different metallic glasses when annealing at temperature below Tc=350 °C, while Kσ is practically constant (≈500 J m−3) in the annealing temperature range from 350 to 525 °C. On the other hand, the magnetostriction constant, λs, was determined as a function of the measuring temperature within the range from 4.2 K up to 600 K. The results can be well accounted for by the single-ion model up to 350 K, while above this temperature the contribution of two-ion mechnism is also inferred.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354556
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  • 119
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    Antiferro-ferromagnetic transition and microstructural properties in a sputter deposited FeRh thin film system (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 3328-3332 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic and microstructural properties are studied in sputter deposited Fe100−xRhx alloy (28.0〈x〈57.0) thin films. As-deposited films show a preferred (111) oriented fcc phase at x(approximately-greater-than)35.0. Annealing at 600 °C results in the CsCl type structure which exhibits a preferred (110) orientation with the same lattice constant as that of bulk. However, an incomplete antiferro-ferromagnetic transition with large thermal hysteresis is observed in a wider composition range (x(approximately-greater-than)45.4) than bulk. Furthermore, magnetization at room temperature decreases continuously from x=35.0 to x=57.0 in contrast to the sharp drop at x=50 in bulk. By using scanning and transmission electron microscopy and Mössbauer spectroscopy, it is found that the retained fcc phase and compositional fluctuation strongly affect the magnetic transition. The retained fcc phase surprisingly reduces the grain growth of the CsCl type ordered phase from 4000 to 300 A(ring) as the Rh content increases from 45.4% to 54.0%.
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    URL: http://dx.doi.org/10.1063/1.354557
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  • 120
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    Thermal pulse study of the polarization distributions produced in polyvinylidene fluoride by corona poling at constant current (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 3357-3365 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A thermal pulse study of the polarization profiles in samples of 12-μm-thick, biaxially oriented polyvinylidene fluoride after corona poling under approximately constant-current conditions, using a modified corona triode in atmospheric air, is reported. An electrical characterization of the corona triode is also reported to show how it may be operated in the constant-current mode. Samples poled without electrode on the corona-exposed surface show polarization distributions sensitive to the corona polarity, with polarization depletion on the corona side of the samples when the corona is positive. Polarization-reversal experiments show switching inhomogeneities with a pronounced dependence on the initial corona polarity. The above observations are consistent with a simple model in which positive charges from the positive corona partially penetrate the sample during poling and cause an inhomogeneous reduction of the poling field.
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    URL: http://dx.doi.org/10.1063/1.354561
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  • 121
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    Thermal stability of internal electric field and polarization distribution in blend of polyvinylidene fluoride and polymethylmethacrylate (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 3366-3372 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It is confirmed that a melt-quenched and annealed blend of 80 wt % polyvinylidene fluoride and 20 wt % polymethylmethacrylate has the β-crystal form of PVDF with optical clarity and other properties that are desirable for a host material in a guest-host system where the guest is an optically nonlinear dye that is orientationally stabilized by the strong internal electric field of a poled ferroelectric. Combined measurements, in such a blend, of the internal electric field Ei, the pyroelectric coefficient Cpyro, and the polarization distribution after electrically poling and subsequently thermally aging for 2 h intervals at temperatures up to 120 °C are reported. Ei and Cpyro increase with increasing poling field Ep. Ei was found to be as large as three times Ep. An unexpected thermal stability of Ei was observed at annealing temperatures above the glass transition temperature of 60 °C up to 100 °C when significant loss of Cpyro was measured. Thermal pulse results yield polarization distributions that may be attributed in part to dipolar polarization and in part to space charge. The prolonged thermal stability of Ei is ascribed to space charge that does not contribute to Cpyro. The poled blend shows second-harmonic generation with a nonlinear coefficient d33 of around 1 pm/V (9×10−9 esu).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354562
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  • 122
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    Piezoelectric, dielectric, and elastic properties of poly(vinylidene fluoride/trifluoroethylene) (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 3394-3398 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The symmetry-predicted nonzero components of the piezoelectric coefficient, dielectric constant, and elastic compliance matrices have been determined on poly(vinylidene fluoride/trifluoroethylene)(75/25) copolymer at room temperature and a frequency of 500 Hz. The temperature dependence of each of the complex piezoelectric coefficients and complex dielectric constants has been measured in the temperature range of −100 to 65 °C. The frequency dependence of these coefficients has also been measured at room temperature. It is found that the relaxation observed in the tensile piezoelectric coefficients of this material is different from that of the dielectric constants, whereas the relaxation of the piezoelectric shear constants shows behavior similar to that of the dielectric constants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354566
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  • 123
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    Hot-stage transmission electron microscopy studies of phase transformations in tin-modified lead zirconate titanate (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 3406-3413 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The temperature dependence of phase stability for tin-modified lead zirconate titanate solid solution ceramics Pb(0.98)Nb0.02[(Zr1−x, Snx)1−yTiy]1−zO3 (PZST) was investigated by hot-stage transmission electron microscopy. Compositions studied included, a material that was antiferroelectric (AFE) at room temperature with x=0.42 and y=0.04, and a material that was ferroelectric (FE) at room temperature with x=0.43 and y=0.08 (abbreviated as PZST 42/4/2 and 43/8/2, respectively). PZST 42/4/2 was found to exhibit a sequence of phase transformations on heating of AFE–multicell cubic (MCC)–simple cubic (SC), whereas PZST 43/8/2 had a sequence of FE-AFE-MCC-SC. Previously referred to F spots (i.e., 1/2[111] superlattice spots) were observed in all four phases. The diffraction intensities for the F spots decreased with increasing temperature, and eventually disappeared above 300 °C. Electron diffraction confirmed the presence of the MCC phase which was characterized by the existence of weak 1/2[110] superlattice spots in the temperature region between the AFE and SC phases. In each composition the AFE phase was characterized by arrays of one-dimensional antiphase domain boundaries and (1/x)[110] superlattice spots. The modulation wavelength for the superlattice spots was found to be a strong function of temperature and was incommensurate with the lattice. The thermal stability of phases in the crystalline solution PZST system is discussed in terms of the observed microstructural features.
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    Optical properties of CdTe: Experiment and modeling (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 3435-3441 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The optical response of CdTe in the 1.1–5.6 eV photon-energy range at room temperature has been studied by spectroscopic ellipsometry. The measured ε(E) data reveal distinct structures at energies of the E0, E1, E1+Δ1, and E2 critical points. These data are analyzed using various theoretical models, namely the model dielectric function (MDF), harmonic-oscillator approximation (HOA), and standard critical-point (SCP) model. Results are in satisfactory agreement with the MDF calculations over the entire range of the photon energies. The HOA (five oscillators) cannot successfully explain the peculiar experimental ε(E) data. The SCP model can provide satisfactory fits to the derivatives of ε(E), but does not yield good fits to ε(E). Dielectric-related optical constants of CdTe, such as the complex refractive index, the absorption coefficient, and the normal-incidence reflectivity, are presented and analyzed. Results of the chemical surface-treatment effect on the pseudodielectric functions have also been presented.
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    URL: http://dx.doi.org/10.1063/1.354543
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    Optical properties of polycrystalline Cd1−xMnxTe (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 3459-3463 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Bulk polycrystalline cadmium manganese telluride, Cd1−xMnxTe, was manufactured in several compositions by a synthesis process. The structure of the obtained compounds was the characteristic zinc-blende polycrystalline pattern being the grain size 100±20 nm. These materials are manufactured to replace single-crystal compounds in some magneto-optical devices. The cut-off wavelength and the Verdet constant are the same as the single-crystals with identical composition. A polarized laser beam, after having passed through a sample of 0.76 mm thickness, was depolarized less than 2.5%, and 90% of its energy was spread into a 2° cone. Scattering of light is produced because of the polycrystalline structure of these compounds. Some scattering diagrams, due to the diffraction and Mie scattering in the polycrystalline grains are shown.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354521
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    Complex magneto-optical Kerr rotation of Fe,FeCo/Cu multilayer films (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 3470-3474 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The complex magneto-optical Kerr rotation spectra of Fe/Cu and FeCo/Cu bilayers and compositionally modulated films (CMF) were studied experimentally and theoretically. In the bilayers, an enhancement of Kerr ellipticity εk by a factor of 5 was observed at long wavelength side, while the Kerr rotation θk can only be enhanced by a factor of 2 around the plasma edge of Cu. In the CMFs, εk was enhanced by 60% but no θk enhancement was observed. Theoretical analyses showed that both the magnitude of effective ε˜xye and the magnitude and signs of effective Ae and Be are important for magneto-optical enhancement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354523
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    Low-energy contributions to positron implantation (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 3479-3496 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A detailed knowledge of low-energy positron implantation is of considerable importance for depth profiling and data analysis in slow positron experiments. Existing Monte Carlo models are capable of simulating the behavior of positrons incident at keV energies, then following the energy-loss process to final kinetic energies of from 20 to 100 eV. A Monte Carlo calculation of the final stages of positron thermalization in Al, Cu, and Au, from 25 eV to thermal energies, is described via the mechanisms of conduction-electron and longitudinal acoustic-phonon scattering. This calculation produces a wide variety of data, including implantation profiles, fraction and energy distribution of reemitted positrons, and the mean thermalization time. A way to obtain information about positron energy loss by considering the time evolution of a point concentration (delta-function distribution) of positrons is described. Diffusion coefficients are obtained that are in good agreement with experiment. The effects of a positive positron work function are examined in the context of a positron Monte Carlo calculation. It is shown that the latter stages of thermalization can have important effects on the stopping profiles and mean depth. In particular, calculated stopping profiles and mean implantation depth are not adequately described by the Makhovian distribution, in agreement with recent experimental findings. A parameterization of these profiles is provided which will be of use in the analysis of experimental data.
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    URL: http://dx.doi.org/10.1063/1.355282
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    Hydrogen absorption and disproportionation of melt-spun Nd–Fe–B ribbons (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 3514-3518 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Hydrogen absorption and disproportionation of melt-spun Nd–Fe–B-based ribbons are significantly affected by quench state (wheel speed). The initial hydrogen absorption temperature corresponding to the formation of the Nd2Fe14BHx-type phase shifts from ∼120 °C for ingot to 250–300 °C for ribbons spun at 13, 15, 17, 20, 22, and 24 m/s wheel speeds. This shift is presumably related to the fact that ribbons are considerably more inert than ingot, which is typical of Nd–Fe–B materials. The hydrogen disproportionation temperature, however, monotonically decreases with increasing wheel speed from (approximately-greater-than)700 °C for ingot to 530 °C for 24 m/s ribbons. Hydrogen absorption due to disproportionation exhibits a two-step feature for wheel speeds ≥20 m/s. The onset and size of the lower temperature step correlates with the presence and amount of an amorphouslike component in the x-ray diffraction spectra of as-spun ribbons. The amorphouslike component is detectable only for wheel speeds ≥20 m/s, and both the amount of amorphouslike component and the size of the lower temperature step in the hydrogen absorption increase with increasing wheel speed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355317
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    Formation of highly uniform and dense diamond microcrystal thin films using a combustion flame surrounded by an inert-gas flow (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 3531-3533 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An inert-gas curtain method, in which a combustion flame of oxygen/acetylene mixture is protected from the air by a surrounding inert-gas flow, has been developed for the deposition of microcrystalline diamond films. As a result, highly uniform and highly dense microcrystal films of diamonds possessing the quality of natural diamond were successfully prepared. The inert-gas flow allows the hydrocarbon radicals in the flame to be varied for preferential deposition of diamonds.
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    URL: http://dx.doi.org/10.1063/1.354530
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    Nonlinear transition shifts in magnetic recording due to interpattern proximity effects (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 3546-3550 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A high-precision measurement of the proximity shift on a magnetic transition due to the presence of an old transition in the background is presented. Using peak detection electronics, this interpattern shift was deduced by measuring the distance between a reference and a test transition in a multibit pattern, with and without a background transition in the vicinity of the test transition. The measurement process was carefully designed to achieve high accuracy. The proximity shift of a 3380-type write head on disks with different remenent-thickness product for cases of both easy and hard transition types was measured for both the background and the data transitions. Results showed three distinct transition-shift behaviors depending on the background-to-test intertransition distance: a gradual decay in the far region ((approximately-greater-than)2 μm), a rapid rise in the intermediate region, and asymptotic saturation at the near region when the two transitions are almost on top of each other. The asymptotic shift magnitude agrees well with independently measured hard-transition shifts, and good agreement with theoretical modeling is obtained for shifts in the far and intermediate regions.
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    URL: http://dx.doi.org/10.1063/1.354533
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    Millimeter-wave detection by YBaCuO step-edge microbridge Josephson junction (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 3567-3571 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Millimeter-wave detection was investigated using a step-edge microbridge Josephson junction fabricated by a YBaCuO thin film for both the video detection and harmonic mixing detection. Current–voltage (I–V) characteristics, which could be described by the resistively shunted junction (RSJ) model, were obtained up to 70 K with the IcR product of 150 μV at 70 K. The responsivity and noise equivalent input power were calculated as 2400 W/V and 4.4×10−14 W/(square root of)Hz, respectively, in the video detection assuming the RSJ model approximation. Clear dependence of the intermediate frequency output on the applied dc bias voltage was observed in the harmonic mixing detection with the harmonic numbers of 5–16, reflecting the change of dynamic resistance at the constant voltage steps induced by the local oscillation signal on the I–V curve. A minimum detection power of −59.4 dB m and a conversion efficiency (η) of −49.6 dB were obtained for the harmonic number (N) of 5 at 60 K. The relationship between the η and N was expressed as η∝N−2.2.
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    Blue-light electroluminescence from p-phenylene vinylene-based copolymers (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 3584-3586 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electroluminescence (EL) in the blue region of the spectrum with a maximum at 465 nm was observed from polymer films sandwiched between indium-tin-oxide and Al electrodes. The specially designed soluble multiblock copolymers used consisted of chromophoric units that have uniform conjugation length and are spaced with polymethylene units of various lengths. EL originates from the radiative decay of the chromophore singlet excitation created as a result of the recombination of injected charge carriers.
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    A new stable ferromagnetic phase in Nd-Fe-B magnets and its effect on coercivity (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 3596-3598 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The microstructure and coercivity of NdxFe93−xB7 (x=16–28) sintered magnets were systematically studied. A new stable ferromagnetic phase with a composition of NdFe2Ox (x≈0.3) and a Curie temperature of 145 °C is found in the intergranular regions of the magnets, owing to the introduction of oxygen in the magnet processing. It forms at ∼650 °C and its volume fraction reaches a maximum of ∼4% in the Nd22Fe71B7 magnets. The coercivity is considerably enhanced by the appearance of this new phase.
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    Temporal synchronization of independently frequency tunable dual CO2 laser pulses (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 3599-3601 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We describe a new method for the simultaneous emission of two CO2 laser pulses from a single transversely excited atmospheric discharge. The transient gains of the pulsed low-pressure sections of two spatially separate hybrid cavities aligned on the discharge were temporally manipulated to allow low-jitter pulse synchronization. Independently frequency tunable dual laser pulses over arbitrarily selected rotational transitions spanning the available P and R branches of the 9 and 10 μm CO2 laser transitions were obtained, overcoming limitations on possible dual frequency combinations that restricted previous techniques. The result of numerical calculations for the hybrid laser, using a four-level rate equation model, supports the observed delay characteristics and provides a physical basis for understanding the dynamics of the synchronization.
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    URL: http://dx.doi.org/10.1063/1.354495
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    Photorefractive effect in a poled polymer containing the tricyanovinylcarbazole group (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 3617-3619 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The photorefractive properties of a poled polymer containing the tricyanovinylcarbazole group with an alkylene spacer are investigated by four-wave mixing experiments and Mach–Zehnder type electro-optic measurements. The photorefractive effect is demonstrated in a polymer that shows both the photoconductivity and the electro-optic effect intrinsically.
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    URL: http://dx.doi.org/10.1063/1.354501
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    Comment on "Evaluation of the minority carrier diffusion length and edge surface-recombination velocity in GaAs p/n solar cells'' [J. Appl. Phys. 72, 2919 (1992)] (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 3620-3621 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The recent findings of Hakimzadeh, Möller, and Bailey [J. Appl. Phys. 72, 2919 (1992)] regarding the determination of minority carrier diffusion length from electron-beam-induced current data are compared to the results of an earlier study by Luke, von Roos, and Cheng [J. Appl. Phys. 57, 1978 (1985)]. The differences are briefly discussed.
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    Speed properties of a semiconductor-discharge gap IR image converter studied with a streak camera system (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2159-2166 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Under certain experimental conditions a semiconductor-discharge gap structure can be used as detector for spatiotemporal resolved measurements on IR radiation. With a streak camera system and a semiconductor laser diode (λ=1.3 μm), we investigate experimentally the speed properties of this kind of converter. The experimental results are compared with the predictions of a simple theoretical model.
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    A numerical analysis of the double periodic reflection metal grating for multiquantum well infrared photodetectors (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2192-2196 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Two normalized parameters (i.e., s=λ/g and h=a/g, where g is the grating period and a is the width of metal dot) are introduced to characterize the two-dimensional (2D) double periodic reflection metal grating coupler for a multiquantum well infrared photodetector (QWIP). The "method of moments'' is used to analyze this square metal grating structure for coupling the normal incident infrared (IR) radiation into the quantum wells. The main advantage for such a grating structure is that the coupling of the normal incident IR radiation is independent of its polarization direction. Two universal graphs relating the higher-order diffracted power and diffracted angle to the normalized wavelength have been constructed for the design of 2D metal grating coupled QWIPs. By using a simple scaling rule, the coupling quantum efficiency versus wavelength over a broad IR spectrum can be obtained for the grating coupled QWIPs.
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    Fission-fragment excitation of the high-pressure atomic neon laser at 703.2 and 724.5 nm (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2203-2207 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The results of a parametric investigation of the high-pressure fission-fragment excited atomic neon laser operating on the 703.2-nm (3p[1/2]1→3s[3/2]20) and 724.5-nm (3p[1/2]1→3s[3/2]10) transitions in He/Ne/Ar and He/Ne/Kr gas mixtures are reported. The highest measured power efficiency was 0.12% using a 1550-Torr He/Ne/Kr (17/75/8) gas mixture at a pump power of 1 kW/cm3. The power efficiency and the ratio of the 703.2- to the 724.5-nm laser output as a function of total pressure, He/Ne ratio, and percent of Ar or Kr will be discussed.
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    Experimental considerations concerning the velocity measurement of the relativistic electron beam in a gyrotron by means of Thomson scattering (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2229-2236 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The feasibility of Thomson scattering to determine the beam velocity in a gyrotron has been analyzed and preliminary experiments to implement such a system on our 100 GHz quasi-optical gyrotron are reported. Although the project had to be abandoned due to technical problems, the conclusions are that for the 90° scattering arrangement discussed it should be possible to determine at least one velocity component with an acceptable signal-to-noise ratio.
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    URL: http://dx.doi.org/10.1063/1.354704
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    Output characteristics of a discharge-pumped F2 laser (157 nm) with an injection-seeded unstable resonator (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2241-2246 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: To improve beam quality, an injection-seeded unstable resonator was applied to a discharge-pumped F2 laser, which is normally dominated by amplified spontaneous emission with a large beam divergence when using a normal stable cavity, due to the laser's extremely high gain (a small-signal gain-length product ∼29). The time-dependent injection-seeding efficiency was obtained for various injection timings by measuring a ratio of the output laser intensity with the same polarization as the seed laser. Correlation of the injection-seeding efficiency with the temporal evolution of the laser-beam divergence was also studied. Both the time-dependent beam divergence and the injection-seeding efficiency showed degradation at a later part of the laser pulse.
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    URL: http://dx.doi.org/10.1063/1.354706
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    Temperature measurements of a neon Z-pinch plasma (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2260-2267 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A neon Z-pinch plasma, appropriate for sodium/neon photopumping experiments, is studied in detail using temporally, spatially, and spectrally resolved measurements of Ne VII, Ne VIII, and Ne IX emissions. The neon is imploded with a 1 μs rise time, 150–180 kA peak current pulse. Two successive implosions are identified. The first implosion produces a 1-mm-diam plasma with an electron density of 9×1019 cm−3 and a temperature of 200 eV. The second implosion produces a larger diameter (3.5 mm), less dense (7×1018 cm−3) plasma with a temperature of 100 eV. A 70% Ne IX ground-state population at the second implosion is deduced from the measurements.
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    Germanium-doped gallium phosphide obtained by neutron irradiation (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2287-2293 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Results of electrical, optical, electron spin resonance and optically detected magnetic resonance studies of thermal neutron irradiated and annealed at 800 °C n-type GaP are presented. Evidence is found to support the view that the main dopant introduced via transmutation of GaP, germanium, occupies cation sites and forms neutral donors. This confirms the possibility of neutron transmutation doping of GaP. Simultaneously, it is shown that germanium is absent at cation sites. Presence of other forms of Ge-related defects is deduced from luminescence and absorption data. Some of them are tentatively identified as VGa-GeGa acceptors leading to the self-compensation process. This observation means that the neutron transmutation as a doping method in application to GaP is not as efficient as for Si.
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    Charged particle flow in plasma-filled pinched-electron-beam diodes (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2274-2286 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Plasma-filled pinched-electron-beam diode experiments have been performed on the Gamble II (1.5 MV, 800 kA, 60 ns) pulsed power generator at Naval Research Laboratory. These plasma-filled diode (PFD) experiments show three phases of behavior: a low impedance phase followed by a phase of rapidly increasing impedance that culminates in a relatively constant vacuum impedance phase. The duration of the low impedance phase as well as the final operating impedance depends on the prefill plasma density. The charged particle flow in the PFD is studied with one-dimensional (1-D) and two-dimensional (2-D) simulation models. These simulation models show the formation of growing sheaths at both electrodes during the low impedance phase. The end of the low impedance phase in the simulations coincides with the two sheaths meeting in the center of the anode-cathode (A-K) gap. Based on these observations, an analytic model was developed that treats the low impedance phase as symmetric bipolar sheaths. The analytical model adequately predicts the duration of the low impedance phase predicted by the 1-D simulation model. Differences between the bipolar model and the experiments or 2-D simulations can be explained in terms of magnetized sheaths which enhance the ion current over the bipolar level and cause the sheath to grow faster than the bipolar model. During the rapidly increasing impedance phase, the simulations show that the cathode sheath quickly expands to completely fill the A-K gap. At this time, charged particle flow in the simulation models are consistent with the vacuum gap spacing. Experimentally, the higher density, longer conduction time, PFD shots exhibited a significantly lower final impedances than predicted by 2-D simulations. This difference is probably caused by expanding electrode surface plasmas produced by the interaction of the plasma source with one or both electrode surfaces.
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    Raman scattering study on the effects of Ga ion implantation and subsequent thermal annealing for AlSb grown by molecular-beam epitaxy (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2300-2305 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Radiation damage and its recovery process of molecular-beam epitaxy grown AlSb implanted with Ga ions is studied using Raman scattering for Ga ion fluences ranging from 1×1013 to 5×1014 cm−2 and for annealing temperatures ranging from 300 to 600 °C. With increasing fluences the AlSb longitudinal optical (LO) phonon mode shifts to lower frequency and exhibits an asymmetric broadening. Recovery of radiation damages in the ion implanted AlSb is observed after annealing at as low as 300 °C. On the other hand, after annealing at above 500 °C, disordering of the crystalline structure due to the outdiffusion of Sb is observed. The damage states and the recovering behaviors are quantitatively estimated using the spatial correlation model on the LO mode.
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    URL: http://dx.doi.org/10.1063/1.354714
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    Enhancement of magnetic moment of iron atoms in the Fe/Au nanomultilayers (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1929-1932 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Fe/Au multilayers were prepared by alternative vapor deposition. The periodicity, thickness, chemical composition, microstructure, and the magnetic moment of the films were determined and measured by various methods. The magnetic moment per Fe atom in Fe/Au multilayers was considerably enhanced when the Fe layer thickness was thinner than 8 nm and it was up to 2.59 μB, i.e., about 1.2 times of that of bulk Fe, at an Fe layer thickness of 4.5 nm. The experimental results also revealed that as the thickness of the Fe layer decreased, there was an increasing tendency towards perpendicular magnetization in the Fe/Au multilayers. The possible mechanism responsible for the modification of magnetic properties is also discussed.
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    URL: http://dx.doi.org/10.1063/1.355326
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    Observation of nuclear diffraction from multilayers with a Fe/57Fe superstructure (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1933-1937 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nuclear diffraction from a 57Fe5B4C/Fe5B4C multilayer has been observed. The reflectivity was measured by Mössbauer spectroscopy in grazing incidence geometry. A pure nuclear Bragg peak showed up at the expected position in the rocking curve. The energy dependence of the reflectivity was measured at different angles near the Bragg peak. The measurements are in good agreement with the theory. The use of nuclear resonant multilayers as monochromators for synchrotron radiation is discussed.
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    URL: http://dx.doi.org/10.1063/1.354776
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    Contributions to the dielectric constant of the system BaLn2Ti4O12 from packing fraction and nephelauxetic ratio (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1968-1971 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An attempt has been made to identify the optimum parameters for good dielectric resonator materials. The dependence of dielectric constant of the system BaLn2Ti4O12 (Ln=La, Pr, Nd, Sm) on packing fraction and nephelauxetic ratio is discussed. The reported dielectric data for this system were treated using the multiregression method.
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    URL: http://dx.doi.org/10.1063/1.354755
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    Depth-resolved measurement of lattice relaxation in Ga1−xInxAs/GaAs strained layer superlattices by means of grazing-incidence x-ray diffraction (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2381-2387 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The state of relaxation in two different superlattices (SLs) of a system with large lattice mismatch, Ga0.8In0.2As/GaAs grown on GaAs [001] by molecular beam epitaxy, has been investigated by surface-sensitive grazing-incidence diffraction (GID). The SL is squeezed between the substrate and a thick GaAs top layer. The thickness of individual GaInAs layers ta (active layer) is the same in both samples, while the GaAs barrier thickness tb is different. We have studied the influence of the thickness ratio tb/ta on the state of relaxation for different distances from the sample surface. We find that for thick barriers the whole SL remains coherently strained and for the thinner barrier thickness the SL is partially relaxed against the the GaAs top layer. The GID technique was applied for the first time to obtain depth resolution of the lateral lattice parameter in a SL. It is demonstrated to be especially well suited for SL systems with a small difference of the average electron density between the sublayers. The scattering contrast is improved by measuring the intensity as a function of the exit angle ("rod scans'') from the "weak'' (200) Bragg reflection. Comparing computer simulations with the measured variation of the scattering contrast between GaAs and GaInAs layers obtained from different "information depths'' and at different angular positions of the in-plane rocking curves, the state of relaxation can quantitatively be evaluated. On the basis of these results we propose two models for the partial relaxation of the SL into the state of strain-reduced domains. We believe that the partial relaxation is due to the elastic field interaction between the GaInAs layers accross the GaAs barriers, if tb is small.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354724
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    Measurement of interface strength by the modified laser spallation technique. I. Experiment and simulation of the spallation process (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2388-2396 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Part I of this paper presents the modified laser spallation technique for measuring the tensile strength of planar interfaces, using a Doppler displacement interferometer. In this technique, a laser-produced compressive stress pulse in the substrate, reflecting from the coating's free surface pulls the interface in tension and leads to its failure if the tensile amplitude is high enough. The current technique is an improvement over the previous one, since the interface stress is determined directly by recording the coating or substrate free-surface velocities using a laser displacement interferometer. The recorded surface velocity is related to the interface stress via an elastic wave equation simulation. The process of coating spallation is investigated, and the effect of the stress pulse profile and the coating and substrate characteristics on the interface tensile stress is studied using the simulation. Several interface stress charts are given for wider applicability of the modified technique.
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    URL: http://dx.doi.org/10.1063/1.354698
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    Measurement of intrinsic stresses during growth of aluminum nitride thin films by reactive sputter deposition (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2411-2414 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Real-time measurements of intrinsic stresses during growth of polycrystalline and epitaxial aluminum nitride (AlN) thin films on Si(111) are reported. Our room-temperature measurements on polycrystalline films corroborate previous post-growth measurements. Our high-temperature measurements provide evidence of large intrinsic stresses during epitaxial growth of AlN on Si(111) and insignificant stress relaxation during growth.
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    URL: http://dx.doi.org/10.1063/1.354701
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    The 900 °C upper yield stress of Czochralski silicon single crystals with carbon concentrations of 4.0×1014 and 3.5×1015 cm−3 (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2420-2424 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In order to investigate the influence of carbon on the high-temperature strength of Czochralski silicon single crystals, we measured the 900 °C upper yield stress of crystals containing carbon at concentrations of 4.0×1014 cm−3 ("low C'') and 3.5×1015 cm−3 ("standard C''). Prior to testing, all crystals were heat treated for 20 h at 700 °C. They were then annealed at 1000 °C for periods between 1.5–7 h. During the longest anneal, the interstitial oxygen content fell from 2.0×1018 to 1.0×1018 cm−3 in low C crystals and from 1.9×1018 to 7×1017 cm−3 in "standard C'' crystals. The 900 °C upper yield stress of 7 h annealed low C crystals is 13 MPa, which is 30–40% higher than that measured in standard C crystals. The precipitate density, measured optically, is 4×105 cm−2 in low C samples and 9×105 cm−2 in standard C crystals. In all cases, the precipitates punched out dislocations. A model that assumes that the higher interstitial oxygen content retained by the low C crystals results in higher locking stresses for glide dislocations can quantitatively account for these observations.
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    Shock-induced mechanisms of phase transformation from rhombohedral BN to cubic BN (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2440-2444 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Rhombohedral forms of layered boron nitride (r-BN) as mixtures with copper powders were shock compressed and quenched from pressures in the range 8–50 GPa. Recovered specimens were investigated by x-ray diffraction and electron microscopy. The graphite-like BN (h-BN) and turbostratic BN (t-BN) phases are observed in the pressure range 8–22 GPa and wurtzite-type BN (w-BN) in the range 17–39 GPa. The zincblende-type BN (c-BN) phase is identified from specimens subjected to high shock temperatures and consists of very fine grains mostly less than 10 nm. The mechanism of phase transformation of r-BN to c-BN is proposed to occur through two paths: (i) direct conversion by relatively strong shocks and (ii) indirect, kinetically controlled conversion via intermediate phases by shock loadings generating relatively weak pressures (〈50 GPa). The possible intermediate phases are h-BN, t-BN, and w-BN.
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    Al–Ga interdiffusion, carbon acceptor diffusion, and hole reduction in carbon-doped Al0.4Ga0.6As/GaAs superlattices: The As4 pressure effect (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2450-2460 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Al–Ga interdiffusion, carbon acceptor diffusion, and hole reduction were studied in carbon doped Al0.4Ga0.6As/GaAs superlattices (SL) annealed under different ambient As4 pressure conditions in the temperature range of 825 °C–960 °C. The SL were doped with carbon to an initial acceptor concentration of ∼2.9×1019 cm−3. Al–Ga interdiffusion was found to be most prominent under Ga-rich annealing ambient conditions, with interdiffusivity values, DAl–Ga, turned out to be about two orders of magnitude smaller than those predicted by the Fermi-level effect model. Under As-rich ambient conditions, the DAl–Ga values are in approximate agreement with those predicted by the Fermi-level effect model. The hole concentrations in the SL decreased significantly after annealing under As-rich and As-poor ambient conditions, while those after annealing in the Ga-rich ambient were almost totally intact. By analyzing the measured hole concentration profiles, it has been found that both carbon acceptor diffusion and reduction have occurred during annealing. Both the carbon acceptor diffusivity data and the carbon acceptor reduction coefficient data are characterized approximately by a dependence on As4 pressure values to the one-quarter power. These As4 pressure dependencies indicate that carbon diffuses via the interstitialcy or interstitial–substitutional mechanism, while hole reduction is governed by a carbon acceptor precipitation mechanism.
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    URL: http://dx.doi.org/10.1063/1.354682
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    Brillouin scattering by localized acoustic modes in silicon-oxynitride–fused-silica optical waveguides (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2475-2480 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Brillouin scattering connecting guided optical modes is used to study the acoustic waves in a silicon-oxynitride–fused-silica double layer deposited onto a Si substrate. The frequencies of the acoustic modes as derived from the acoustic wave equation are found to reproduce those of the experiment. The scattering intensities are in agreement with a calculation based on the coupled-waveguide-mode formalism with due account of the elasto-optic effect and the corrugation of the surface and silicon-oxynitride–silica interface. Finally, the sound velocities and Pockels coefficients of the silicon-oxynitride layer are determined.
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    URL: http://dx.doi.org/10.1063/1.354685
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    Surface segregation effects of In in GaAs (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2481-2485 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoluminescence (PL), secondary-ion mass spectroscopy (SIMS), and cross-sectional transmission electron microscopy (TEM) measurements have been performed to assess surface segregation of In in GaAs during molecular-beam epitaxial growth of InAs monolayers between GaAs layers. The InAs growth temperature at which In segregation is detectable depends on the characterization technique used; using PL it is above 420 °C, but from TEM and SIMS it is 420 and 340 °C, respectively. These results highlight the need for complementary information to provide a better understanding of the segregation phenomenon. SIMS data show that the total amount of In segregating and the extent of its distribution both increase with InAs deposition temperature.
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    URL: http://dx.doi.org/10.1063/1.354686
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    X-ray diffraction characterization of ternary artificial superlattices (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2501-2506 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin films of alternating Au, Ag, and Cu wedge-shaped metal layers were made by magnetron sputtering in order to develop a method for investigation of a multicomponent systems. X-ray-diffraction patterns of all as-deposited samples revealed satellites in the vicinity of (111) reflections, evidence of composition-modulated artificial superlattice formation. The experimental spectra are well explained by the kinematical diffraction theory for imperfect superlattices. Computer simulations have demonstrated extremely high sensitivity to the fluctuations ΔH/H of the superlattice period H. As a result, a rapid and simple method of ΔH/H determination is proposed.
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    Bulk and interface stresses in silver-nickel multilayered thin films (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2517-2523 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Stresses were measured in 〈111〉-textured Ag/Ni multilayered thin films from the substrate curvature and from lattice parameter measurements by x-ray diffraction. The difference between the total multilayer film stress and the layer deposition stresses can be attributed to a tensile interface stress of −2.27±0.67 J/m2. Interfacial phase formation is unlikely in this system as indicated by the exceptionally low mutual solubilities.
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    Critical epitaxial thicknesses for low-temperature (20–100 °C) Ge(001)2×1 growth by molecular-beam epitaxy (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2512-2516 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The growth of Ge(001) by molecular-beam epitaxy at temperatures Ts between 20 and 100 °C, and deposition rates of 0.5 and 1 A(ring) s−1, was investigated using a combination of in situ reflection high-energy electron diffraction and post-deposition cross-sectional transmission electron microscopy. All films consisted of three zones beginning with a defect-free epitaxial layer of thickness t1 in which ln(t1)∝(1/Ts). The second zone was a narrower intermediate layer containing {111} stacking faults and microtwins, while the third zone was amorphous. An atomistic growth model is proposed to explain the observed morphological breakdown during low-temperature growth.
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    Theoretical investigation of different formulations of the electron-plasmon interaction under transient conditions (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2550-2556 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a comparison of two different methods of including the electron-electron long-range interaction on the dynamics of hot electrons in degenerate GaAs under transient conditions in two different hot electron transistor structures of 60- and 120-nm base widths, respectively. The first approach is quantum mechanically based while the second follows a semiclassical prescription. The calculated energy spectrum, velocity distribution, and percentage of injected carriers collected in the hot electron transistors are determined under three different conditions: the inclusion of the plasmon interaction through the quantum-mechanical formulation, the inclusion of the plasmon interaction through the semiclassical technique, and with no plasmon interaction. The calculated energy spectrums within the two plasmon models are qualitatively similar. They differ only by the extent to which the peaks are broadened and the absolute ratio of collected to injected carriers. Because of the very different energy relaxation within the plasmon models, the ratio of collected to injected electrons is predicted to be far smaller using the quantum-mechanical model than the semiclassical model. Subsequently, knowledge of the absolute ratio of the collected to injected carriers in a hot electron transistor would give some indication of the appropriateness of each model.
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    URL: http://dx.doi.org/10.1063/1.354696
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    Real-time spectroellipsometry investigation of the interaction of silane with a Pd thin film: Formation of palladium silicides (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2535-2542 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present the application of spectroscopic phase modulated ellipsometry to the study of both ultrafast and slow processes of the interaction of silane (SiH4) with thin films of palladium. Changes of the optical properties of thin films exposed to different SiH4 fluxes are monitored by in situ single wavelength ellipsometry in the case of high fluxes which lead to ultrafast processes and by in situ spectroscopic ellipsometry at low fluxes and slow kinetics. The study of the interaction of SiH4 with Pd at 250 °C reveals the complicated character of the process which depends on the flux of silane and leads to the formation of palladium disilicide, palladium hydrides, and an intrinsic porosity. A qualitative model of the process is proposed. The initial stage of the reaction at high fluxes of SiH4 is dominated by a grain boundary diffusion of SiH4 inside the Pd film, followed by the catalytic decomposition of SiH4 and a strong process of an intrinsic formation of porosity. This fast process (duration of 10 ms) proceeds through the formation of a metastable Pd-rich phase. The appearance of the intrinsic porosity enhances the diffusion of SiH4 inside the Pd film, which results in a drastic acceleration of the silicide formation. At low SiH4 fluxes the characteristic time of the reaction increases up to some tens of minutes and proceeds through the formation of both silicide and palladium hydride.
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    Properties of hydrogenated amorphous silicon prepared by alternatively repeating chemical-vapor deposition from disilane and hydrogen plasma treatment (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2543-2549 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Experimental studies have been carried out to characterize hydrogenated amorphous silicon prepared by alternatively repeating chemical-vapor deposition (CVD) from disilane and hydrogen plasma (HP) treatment (referred to as HP treated CVD a-Si:H). It has been found that hydrogen plasma treatment induces structural relaxation of Si network in addition to the passivation of Si dangling bonds. Two types of defect states with different Gaussian energy distribution exist in this material, and this type of distribution has been found to be common in undoped a-Si:H prepared by a variety of methods. High film quality, i.e., a low defect density (〈1016 cm−3) and a fairly long ambipolar diffusion length (0.12 μm), and significant reduction of light-induced changes have been simultaneously achieved in HP treated CVD a-Si:H. Steady state transport of electrons and holes under illumination are controlled by the states other than neutral Si dangling bond state (D0). The behavior of these states with long exposure to light is different from that of D0.
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    Enhanced luminescence due to impact ionization in photodiodes (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2565-2571 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A simple mechanism explaining the enhanced luminescence of p-i-n structures and reach-though avalanche photodiodes approaching reverse-bias breakdown is proposed. The model presented predicts enhanced photon emission based on calculations of the spatial dependence of the impact ionization events. Experimentally, an enhancement of a factor of 100 in the optical efficiency is observed in p-i-n silicon photodiodes when biased in the gain regime. A series of measurements made on commercially available photodiodes are presented. Theoretical predictions are compared with the experimental photonic output versus internal electric field and current.
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    URL: http://dx.doi.org/10.1063/1.354702
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    The enhanced Stark effects of coupled quantum wells and their application to tunable IR photodetectors (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2598-2604 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A tunable asymmetric coupled quantum well far-infrared photodetector is proposed in this paper. The basic asymmetric coupled quantum wells are composed of two quantum wells separated by a thin barrier. In this way, the electron in each well interacts strongly with other electrons to achieve a large Stark tuning effect. The eigenenergies and the wave functions of the quantum-well structures are solved by the self-consistent method, and the effect of the exchange interaction on the ground-state subband has also been taken into account. The absorption coefficient is evaluated by the density-of-states formalism. Based on theoretical calculations, tuning ranges from 8.2 to 11.3 μm and 7.8 to 10.5 μm are predicted for the proposed asymmetric coupled-quantum-well structure and high-low coupled-quantum-well structure, respectively. This tuning capability is achieved by varying the applied electric field in the 20–90-kV/cm range.
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    Optimization of charge transfer to the active channel in δ-doped heterostructures (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2613-2618 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An accurate theoretical model based on the two-band effective-mass-approximation that includes nonparabolic, strain, finite temperature, many-body, and deep donor (DX) center effects is used to investigate the electronic properties of δ-modulation-doped semiconductor heterostructures with the aim of optimizing the active channel density. Inclusion of the DX centers in the model leads to the saturation of the electronic density with increasing δ-doping concentration for both structures doped on one side and structures doped on both sides of the channel. The saturation value in the latter case is almost twice as high as in the former. The self-consistent calculations show that by using a superlattices of superlattices configuration with an appropriately chosen superlattice barrier one can achieve a 50% increase in the maximum charge transfer compared to conventional heterostructures of similar design, without increasing impurity scattering in the channel.
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    Submillimeter wave low-temperature admittance of n-GaAs and n-InP diode structures (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2633-2637 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Numerical simulation results for n+nn+ GaAs and InP diode structures in the 1–5 THz frequency range are presented. Cryogenic temperatures from 4 through about 77 K as well as some cases above liquid-nitrogen temperature are examined to obtain the two-terminal admittance. Earlier work has suggested possible negative conductivity at or below 4.2 K, but nothing consistent above 77 K. Implications of the Monte Carlo data for generation of submillimeter waves at intermediate lattice temperatures between 4 and 60 K are discussed for GaAs. Furthermore, numerical results are obtained at elevated lattice temperatures (200 and 300 K) to form a more complete view of transport in InP. The GaAs and InP results strongly suggest negative conductance behavior will be found below 20 K.
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    The nature of the hole traps in reoxidized nitrided oxide gate dielectrics (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2665-2668 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: To find out the nature of hole traps in reoxidized nitrided oxide (RNO), a series of field and thermal detrapping experiments were performed following irradiation. It has been found that not only are the hole traps in RNO located near the gate-SiO2 interface instead of near the Si-SiO2 interface as in conventional dry oxides, but that the energy distribution of these traps is also quite different from that in conventional oxides. This indicates that the origin of the traps in RNO is different from that normally found in conventional oxides.
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    Dynamic properties of a superconducting quantum interference device containing arrays of Josephson junctions (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2674-2680 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The dynamic properties of a superconducting quantum interference device (SQUID) containing arrays of Josephson junctions in a superconducting loop, and in particular the case of a four-junction SQUID, is analyzed theoretically via computer simulations. It is shown that phase locking of Josephson junctions determines the dynamic behavior of the SQUID. In the case of a stable phase-lock state hysteretic I-V curves as well as unusual voltage-flux dependencies appear. The influence of a small spread in the Josephson junction parameters upon the stability of the phase-lock state is investigated in parameter space.
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    Magnetization reversal processes in Co-Re antiferromagnetically coupled multilayers: A magneto-optic and Monte Carlo study (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2692-2700 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A study of magnetization reversal processes in sputtered antiferromagnetically coupled (CotCoRe5 A(ring))×n multilayers, with n=2,3,5 is reported. The two components of the magnetization, parallel and perpendicular to the applied field are analyzed using a suitable transverse Kerr effect differential magneto-optical setup. At the remanent state, and for n=3, and 5, we obtain a magnetization of 1/3 and 1/5 of the saturation magnetization, respectively. This means that the magnetization in each layer is aligned parallel or antiparallel to the applied field direction. The observed perpendicular magnetization component is as expected, much smaller than the parallel magnetization component over the entire length of the hysteresis cycle. A Monte Carlo simulation was used to study the spin configurations in the individual layers as well as the type of magnetization hysteresis cycles. We find that the introduction of a small uniaxial anisotropy is needed to explain the observed multiloop structure in the n=3 multilayers. Within our model, spin-canting may occur within the ferromagnetic layers leading to particular remanent-state spin configurations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354663
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    High-field effective linewidth and eddy current losses in moderate conductivity single-crystal M-type barium hexagonal ferrite disks at 10–60 GHz (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2705-2718 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The losses associated with the high-field tail region of the ferromagnetic resonance (FMR) absorption curve were investigated at 10, 19, 35, and 60 GHz for 0.10–1.75-mm-thick c-plane circular disks of flux-grown single-crystal M-type barium ferrite materials. A conventional high-field effective linewidth analysis of the data yielded an effective linewidth which increased with the square of the disk thickness and linearly with frequency, dependencies which indicate a predominant eddy current loss process. Based on these results, an eddy current loss analysis of the tail region was done, based on the insulator FMR response and eddy current losses driven by the FMR response. This analysis leads to a new noninvasive technique for the determination of the microwave conductivity in moderate conductivity ferrites. One obtains the conductivity from an appropriate analysis of the FMR absorption tail in the same way that analysis of the magnetic loss tail yields a high-field effective linewidth. Based on this technique, the microwave conductivity of these flux-grown barium ferrite single-crystal materials was determined as a function of frequency and found to increase linearly from 0.033±0.004 Ω−1 cm−1 at 10 GHz to 0.10±0.02 Ω−1 cm−1 at 60 GHz. These results are consistent with a measured dc conductivity of 0.03–0.05 Ω−1 cm−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354665
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    Non-steady-state photoelectromotive force in semiconductor crystals with high light absorption (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2736-2741 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The influence of a high light absorption on the photoelectromotive force excited by moving interference fringes in photoconductive crystals is considered. It is shown that due to a deep penetration of the electric field pattern into the sample volume, the absolute magnitude of the output signal and its dependence on the spatial frequency of the grating may practically be the same as for low absorption. This conclusion is confirmed experimentally for semi-insulating GaAs:Cr for λ=633, 840–900, and 1064 nm. This means, in particular, that films or thin specimens of photoconductive materials can be used for fabrication of adaptive detectors of phase-modulated optical signals with the same efficiency as bulk specimens.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354669
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    Quantitative characterization of modulation-doped strained quantum wells through line-shape analysis of room-temperature photoluminescence spectra (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2760-2767 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Room-temperature photoluminescence (PL) has been used to characterize modulation-doped AlGaAs/InGaAs/superlattice strained layer quantum wells. A phenomenological line-shape model has been developed which can be fitted to PL spectra in order to obtain key parameters such as the subband energies, Fermi energy, and transition amplitudes. Quantum well sheet densities calculated from fits to the PL spectra (taken at both room temperature and 77 K) have been compared to sheet densities obtained from low-temperature Hall measurements. It has also been shown how variations in quantum well composition, width, and symmetry can be characterized by shifts in values of the relevant fitting parameters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355322
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    The Ag/As2S3 photodoping mechanism: Photon absorption (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2768-2770 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The sensitivity of the Ag-photodoping process has been measured as a function of photon energy between 1.9 and 6.4 eV. The sensitivity increases with increasing photon energy except at 3.8 eV (325 nm) where Ag exhibits an anomalous window. At this energy there is an abrupt and large decrease of sensitivity. In a second measurement, the transmission as a function of wavelength between 200 and 900 nm of a 2000-A(ring)-thick film of As2S3 doped with an imaging dose of Ag and a second sample doped with a larger than imaging dose are compared with an undoped sample. Band-gap shrinkage is different for the two doses. Both measurements suggest that under certain conditions, photon absorption in the Ag-photodoping process occurs in the Ag.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354646
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    Exciton luminescence in Si1−xGex/Si heterostructures grown by molecular beam epitaxy (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2790-2805 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Coherent Si1−xGex alloys and multilayers synthesized by molecular beam epitaxy (MBE) on Si(100) substrates have been characterized by low-temperature photoluminescence (PL) spectroscopy and transmission electron microscopy (TEM). Phonon-resolved transitions originating from excitons bound to shallow impurities were observed in addition to a broad band of intense luminescence. The broad PL band was predominant when the alloy layer thickness was greater than 40–100 A(ring), depending on x and the strain energy density. The strength of the broad PL band was correlated with the areal density (up to ∼109 cm−2) of strain perturbations (local lattice dilation ∼15 A(ring) in diameter) observed in plan-view TEM. Thinner alloy layers exhibited phonon-resolved PL spectra, similar to bulk material, but shifted in energy due to strain and hole quantum confinement. Photoluminescence excitation spectroscopy, external quantum efficiency, time-resolved PL decay, together with the power and temperature dependence of luminescence intensity, have been used to characterize Si1−xGex/Si heterostructures exhibiting both types of PL spectra. The role of MBE growth parameters in determining optical properties was investigated by changing the quantum well thickness and growth temperature. The transition from phonon-resolved, near-band-gap luminescence in thin layers to the broad PL band typical of thick layers is discussed in terms of a strain energy balance model which predicts a "transition thickness'' which decreases with increase in x.
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    URL: http://dx.doi.org/10.1063/1.354628
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    Polyimide ablation using intense laser beams (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2830-2833 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The ablation of polyimide by intense UV laser beams is modeled with a photothermal process that considers the shielding of the laser beam by the decomposed polymer. The heating of the decomposed material may drive the polymer degradation process for fluences above several J/cm2.
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    URL: http://dx.doi.org/10.1063/1.354634
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    Effect of graphitic carbon films on diamond nucleation by microwave-plasma-enhanced chemical-vapor deposition (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2841-2849 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Diamond nucleation on very smooth (100) silicon substrates coated with thin films of a colloidal graphite suspension was investigated with a microwave-plasma-enhanced chemical-vapor-deposition system. Nucleation densities of the order of 106 cm−2 were obtained by coating the substrates with carbon films of thicknesses less than 1 μm. However, very low nucleation densities were obtained with carbon film thicknesses greater than 1 μm. The effect of the carbon film thickness on diamond nucleation was examined by measuring the etching rate of carbon films exposed to a hydrogen plasma and was further interpreted on the basis of scanning electron microscopy and Raman spectroscopy results. Etching of the original carbon may lead to the formation of a thin residual carbon film when the initial film thickness is less than a critical value. Results demonstrated that the high nucleation densities of good quality cubo-octahedral diamond crystals obtained with relatively thin carbon films were primarily due to the formation of a porous ultrathin residual carbon film. The critical initial film thickness was a function of the plasma etching and deposition rates of carbon which, in turn, affected the effective local carbon concentration. Thick carbon films yielded insignificant nucleation densities and poor quality diamond because of the high local carbon content resulting from the partial etching of carbon and the increased carbon concentration in the plasma. The local carbon concentration and the residual carbon film are the proposed principal factors for the obtained high diamond nucleation densities on unscratched silicon substrates.
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    URL: http://dx.doi.org/10.1063/1.354636
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    Doping effect of buckminsterfullerene in poly(2,5-dialkoxy-p-phenylene vinylene) (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2860-2865 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoluminescence has been markedly quenched and photoconductivity has been enhanced by more than one order of magnitude upon introduction of several mol% of buckminsterfullerene (C60) to poly(2,5-dialkoxy-p-phenylene vinylene) (RO-PPV), especially at excitations about 2.2 eV, corresponding to the band gap energy of RO-PPV and also in bands at 1.8 and 3.5 eV, which correspond to optical excitation of C60 molecules, suggesting that photo-induced charge transfer occurs between RO-PPV and C60. On the other hand, absorption spectrum and electrical conductivity of RO-PPV have been scarcely influenced by doping of small amount of C60, suggesting that the ground state charge transfer between C60 and RO-PPV is not effective, contrary to the case of poly(3-hexylthiophene). These results are discussed by taking relative electronic energy states of RO-PPV and C60 into consideration. The photo-excited exciton-polaron (Ex-P) in RO-PPV is interpreted to migrate along about 100 monomer units along a polymer main chain in its lifetime and dissociates when encountered with C60. These unique doping characteristics of C60 in RO-PPV are not dependent on the alkyl chain length, contrary to the case of poly(3-alkylthiophene).
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    URL: http://dx.doi.org/10.1063/1.354639
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    Plasma chemistry of He/O2/SiH4 and He/N2O/SiH4 mixtures for remote plasma-activated chemical-vapor deposition of silicon dioxide (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 6538-6553 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Remote plasma-activated chemical-vapor deposition (RPACVD) provides a means to deposit thin dielectric films with low ion bombardment and while having high selectivity in generating precursors. In RPACVD of SiO2, gas mixtures of He/O2 or He/N2O are passed through a plasma, producing radicals and excited states that are mixed with silane downstream. Excited states produced in the plasma and precursor species produced by these reactions then flow to the substrate. Although high-quality SiO2 films can be produced by RPACVD, the gas-phase deposition precursors have not been identified. A two-dimensional plasma chemistry model is described, and results from that model are used in a discussion of possible gas-phase precursors for SiO2 deposition. In particular, the formation and transport of silanols (SiH2O and SiH3O) are examined as a function of gas mixture, power deposition, and geometry. It is found that the fluxes of SiH2O, SiH3O, and SiH3 are sufficient to account for the observed deposition rates; while systematic dependencies of the fluxes of HSiO and SiO discount them as being deposition precursors. He/N2O/SiH4 mixtures differ from He/O2/SiH4 mixtures by providing larger fluxes of SiH3 to the substrate, while the fluxes of SiH2O, SiH3O, and O2(1Δ) are significantly less.
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    URL: http://dx.doi.org/10.1063/1.355115
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    An ordered Ga2Te3 phase in the ZnTe/GaSb interface (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 6566-6570 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A Ga2Te3 interfacial phase has been observed in a ZnTe/(001)GaSb heterostructure by high resolution electron microscopy under special imaging conditions. This phase exists in domains 5–10 nm in size on the ZnTe side of, and usually 2–4 nm away from, the interface. A structural model has been proposed for this phase that is derived from the sphalerite cell with cation sites occupied either fully (occupancy 1) or partially (occupancy 5/9) by Ga atoms. The fully occupied Ga sites form a regular array of uninterrupted chains along the [110] direction of the sphalerite unit cell. The partially occupied Ga sites can also be considered as forming chains containing both Ga atoms and vacancies along the [110] direction. Within these chains vacancies are highly mobile, resulting in an average Ga occupancy of 5/9. The unit cell of Ga2Te3 is orthorhombic with the space group Amm2. The lattice parameters of the unit cell have been derived from electron diffraction data.
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    URL: http://dx.doi.org/10.1063/1.355118
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    The gettering efficiency of a direct bonded interface (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 6576-6579 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In these studies the gettering efficiency of copper at a direct bonded interface is compared to the gettering efficiency of a bulk defect zone formed during a one step and three step annealing process of Czochralski silicon wafers. The gettering efficiency of a bulk defect zone is considerably higher than that of the interface. Thus intrinsic gettering is expected to be effective in gettering direct bonded p-n junctions. Without any intrinsic gettering zone, copper silicide readily precipitates at the bonded interface, forming complex star-shaped colonies. Their morphology changes into single colonies in {110} planes if the wafer pairs are prestressed during contacting at room temperature. In this case the gettering efficiency of the bonded interface increases in comparison to the bulk defect zone. Prestressing experiments have shown that the denuded zone width in tensile stressed regions of a wafer increases.
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    URL: http://dx.doi.org/10.1063/1.355095
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    Current conduction in an implant isolated GaAs/AlGaAs heterostructure (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 6571-6575 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the current-voltage characteristics of an oxygen implant-isolated region of a GaAs/AlGaAs heterostructure between 25 and 295 K. Current conduction was dominated by bulk rather than metal contact limited effects. Bulk conduction in the implant-isolated region is due to several different mechanisms; at low electric fields a resistive current; at low temperatures and high electric fields, field ionization current proportional to V2 exp(−V0/V); and at high temperatures and high electric fields, Poole–Frenkel conduction proportional to V exp(aV1/2/rkT−qφb/rkT). The resistive current can further be separated into two components, one of which dominates at low temperatures and is proportional to V exp(−B/T1/4), and the other which dominates at high temperatures and is proportional to V exp(−Ea/kT). These results are applicable to any GaAs-based structure rendered semi-insulating by an isolation implant, and describe the current conduction characteristics from zero bias to breakdown. Such a description is critical to understanding leakage currents in GaAs/AlGaAs devices such as high-performance heterojunction bipolar transistors, field-effect transistors, and laser diodes that commonly employ implant isolation as a part of the fabrication process.
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    URL: http://dx.doi.org/10.1063/1.355119
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    Defects and ion redistribution in implant-isolated GaAs-based device structures (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 6580-6586 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Implant isolation of thick GaAs based epitaxial structures using either multiple energy keV ions or a single MeV ion implantation is becoming more popular for devices such as heterojunction bipolar transistors or quantum well lasers. We report examples of both types of isolation schemes, using keV F+ and H+ ions, or MeV O+ ions. Post-implant annealing at temperatures in the range 500–600 °C is needed to maximize the resistivity of the implanted material, but this causes redistribution of both F and H (but not O) and accumulation of hydrogen at strained or ion-damaged interfaces. The amount of hydrogen motion is sufficient to cause concerns about dopant passivation occurring in the initially masked, active regions of the devices. The resistance of the ion-implanted regions is stable for periods of ≥50 days at 200 °C, and is controlled by deep level point defects which pin the Fermi level near mid gap.
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    URL: http://dx.doi.org/10.1063/1.355096
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    Measurement of ion induced damage-profiles in GaAs (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 6587-6591 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this study, with the use of a sensitive optical technique, we demonstrate the possibility of measuring the depth distribution of damage in GaAs that is generated by various ion-assisted processes such as ion implantation and ion assisted plasma etching. We have used this technique to measure the depth distribution of damage in both He and Ar implanted GaAs and in inert gas and reactive ion etched GaAs. The sensitivity of the technique allowed us to measure damage profiles over a large range of ion energies and ion doses. We have also confirmed previously published results indicating that damage created by sputter etching is inversely proportional to the mass of the ions used in the etching process.
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    URL: http://dx.doi.org/10.1063/1.355337
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    Pulsed laser-induced melting followed by quenching of silicon films (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 6592-6598 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Amorphization and crystallization were studied through laser-induced melting of silicon films formed on quartz substrates induced by irradiation with a 30 ns XeCl excimer laser. Homogeneous and rapid solidification occurs and amorphous solid state can be formed when the melt duration is long enough to make the temperature gradient in liquid silicon lower than 1×105 K/cm at the Si/quartz interface. The solid state after homogeneous solidification is governed by recalescence caused by latent heat released at solidification. A completely amorphous state is formed when film thickness is thinner than 24 nm because latent heat reduces as film thickness decreases. Both crystalline and amorphous states were observed for film thickness above 24 nm because recalescence can cause crystalline grain growth. Complete crystallization occurs through interface controlled growth when the temperature gradient is higher than 1×105 K/cm. The velocity of liquid/solid interface is 0.6 m/s, which is too low to cause amorphization.
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    URL: http://dx.doi.org/10.1063/1.355097
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    Raman investigation of the nonlinear optical phenomenon of polarization rotation in Ti:LiNbO3 channel waveguides (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1492-1500 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The nonlinear phenomenon of polarization rotation in Ti:LiNbO3 optical channel waveguides was investigated using Raman microprobe microscopy. Polarization sensitive Raman selection rules permitted the identification of polarization rotation of the propagating transverse electric or transverse magnetic waveguide mode. From an analysis of the Raman scattered light collected orthogonal to the waveguide surface the threshold power necessary to initiate the process of mode conversion could be determined. In addition, the Raman microprobe was used to determine waveguide loss coefficients by collecting inelastically scattered light. The values obtained by this method were compared to those measured by collecting the elastically scattered light. A value for the asymmetric component, β15, of the photovoltaic tensor was calculated to be 7.8×10−13 A/W for the X-cut, Y-propagating and 3.8×10−14 A/W and 1.2×10−14 A/W for the rapid thermally annealed Z-cut, Y-propagating channel waveguides, respectively.
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    URL: http://dx.doi.org/10.1063/1.354848
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    Simulation and analysis of silicon electro-optic modulators utilizing the carrier-dispersion effect and impact-ionization mechanism (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1521-1528 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new type of Si guided-wave electro-optic modulator is proposed and analyzed. The modulator makes use of the impact-ionization mechanism for carrier generation, and the carrier-dispersion effect for electro-optic conversion. Both electrical and wave propagation properties of the modulator were examined by a two-dimensional device simulator and a three-dimensional waveguide simulator, respectively. Numerical estimates of phase modulation due to refractive-index change and intensity modulation due to optical absorption and radiation loss were obtained. One of important features of the prospected modulator is speed. The simulated turn-on and turn-off time of the modulator was less than 1 ns. GHz modulation is, therefore, possible for this class of modulators with device structure and doping profiles optimized for fiber coupling.
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    URL: http://dx.doi.org/10.1063/1.354851
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    Thermal diffusivity measurements on solids using collinear mirage detection (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1539-1547 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A report on the adequacy of the collinear mirage technique for thermal diffusivity measurements on bulk homogeneous solids is presented. A 3D theoretical model for collinear deflection has been developed from which two simple linear relations between measurable parameters and the thermal diffusivity have been obtained. Two methods, the so-called zero-crossing and phase methods, are discussed in detail. The second one seems to be a promising tool for thermal diffusivity determination. It has been validated by means of experimental measurements on a set of samples with known thermal diffusivities. The technique is restricted to semitransparent solids but is also valid for materials with either high or low thermal diffusivities, being specially useful for this last group.
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    URL: http://dx.doi.org/10.1063/1.354854
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    Effect of H on Si molecular-beam epitaxy (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 6615-6618 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In Si crystal growth by molecular-beam epitaxy (MBE) at low temperatures there is known to be an epitaxial thickness: an initially crystalline regime before the deposited film becomes amorphous. The predominant impurity in MBE is hydrogen, but the role of background H in low-temperature MBE has not previously been assessed. Here the effect of deliberate dosing of the Si surface with atomic H during low-T growth is studied. The epitaxial thickness is shown to be sensitive to very small additional H fluxes (≈10−9 Torr, i.e., an increase in H only marginally above ambient). With further increases in dose rate, the epitaxial thickness decreases as hepi=h0−k(ln PH). Using secondary-ion-mass spectrometry data on the segregated H at the interface, we argue that breakdown in epitaxy is not caused directly by the surface concentration of adsorbed impurities. It is deduced that very small concentrations of H may influence the Si surface diffusion rate. The possible effect of background H adsorption on previous experiments on Si steps and surface diffusion is discussed.
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    URL: http://dx.doi.org/10.1063/1.355101
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    Annealing of silicon implanted by a high dose of cobalt ions investigated by in situ x-ray diffraction (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1590-1596 
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    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A silicon wafer was implanted by a high dose of cobalt ions. Afterwards it was annealed in situ while grazing incidence x-ray diffraction measurements in a temperature range up to 690 °C were carried out. The formation of cobalt disilicide (CoSi2) precipitates starts during implantation. The annealing dependence of the precipitate growth, of strain relaxation, and of improvements of the silicide crystallinity was determined. We got an activation energy of (0.47±0.08) eV for the observed annealing process. The result is a buried cobalt disilicide layer with very rough interfaces. The film quality can be improved by a subsequent annealing at about 1000 °C.
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    URL: http://dx.doi.org/10.1063/1.354832
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    Ion implantation and dry etching characteristics of InGaAsP (λ=1.3 μm) (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1610-1615 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electrical activation characteristics of Si+ and Be+ ions implanted into InGaAsP (λ=1.3 μm) grown lattice matched to InP by metalorganic molecular beam epitaxy were studied as a function of ion dose (5×1012–5×1014 cm−2), annealing time (3–60 s) and annealing temperature (575–750 °C). Maximum doping concentrations of ∼2×1019 cm−3 were obtained for both Si+ and Be+, with activation energies for electrical activation of 0.58 and 0.39 eV, respectively. Multiple energy F+ or H+ implants can be used to produce high resistance layers for isolation purposes—maximum sheet resistances of ∼8×106 Ω/(D'Alembertian) or ∼106 Ω/(D'Alembertian) for initially p+ or n+ InGaAsP, respectively, were obtained for F+ implants followed by annealing near 450 °C. Smooth, anisotropic dry etching of the InGaAsP is obtained with electron cyclotron resonance CH4/H2/Ar discharges at low dc biases. The etch rates are the same for both n+ and p+ quaternary layers and are independent of the doping level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354809
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  • 191
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    Radiation damage behavior of LiNbO3 crystal by MeV F ion implantation (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1625-1628 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: X, Y, and Z crystalline cut LiNbO3 crystals were implanted by 1.0 MeV F ions with a dose of 1×1015 ions/cm.2 The virgin and implanted LiNbO3 crystals were investigated using the Rutherford backscattering/channeling technique. The obtained minimum yields of virgin crystals were 4%, 8%, and 6% for X-, Y-, and Z-cut LiNbO3 crystals, respectively, because of their different arrangements of lattice sites in channeling direction. The measured damage profiles are also influenced by the arrangement of lattice sites in channeling measurements. The damage profiles of X-cut LiNbO3 crystal induced by 1.0 MeV F+ at a fluence range of 1×1014–3×1015 ions/cm2 have been studied and compared with the Transport of Ions in Matter, version 1990 calculation. It has been found that not only the nuclear energy deposition but also the electronic energy deposition influences the defect production.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354811
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  • 192
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    Stability analysis of numerical solutions of wave propagation when pseudoviscosity is replaced by real viscosity (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1649-1651 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The artificial viscosity method was originally introduced by Von Neuman and Richtmeyer [R. D. Rchtmeyer and K. W. Morton, in Difference Methods for Initial Value Problem (Interscience, New York, 1967)] to spread the shock over several cells of the mesh. This method is useful if the physical phenomena present in the shock front are not of interest. In some cases, such as polymer, the amount of viscosity is large enough to spread the front shock naturally. In our problem, pseudoviscosity is ignored. A stability analysis shows that the time step restrictions for stability can be less stringent than with pseudoviscosity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354815
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  • 193
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    Ion-beam adhesion effects in the Cu/sapphire interfacial system (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1670-1674 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of 2 MeV H+ , B+, O++, and Au++ ion irradiation on the adhesion energy of thin Cu films deposited on sapphire has been investigated. Adhesion energy was measured by the observation of the resultant laterally segregated Cu particle shape after vacuum annealing. Film/substrate adhesion is shown to increase with increasing ion dose and exhibits saturation behavior at high fluences. The adhesion energy is shown to be a linear function of the electronic stopping over the entire ion mass range—suggesting a purely electronic mechanism for the adhesion enhancement in this ion energy regime.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354819
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  • 194
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    Structural and electrical properties of reactively sputtered InN thin films on AlN-buffered (00.1) sapphire substrates: Dependence on buffer and film growth temperatures and thicknesses (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1684-1691 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An extensive investigation of InN overlayers on AlN-buffered (00.1) sapphire by reactive magnetron sputtering has been undertaken and the dependencies of several basic materials properties (film thickness, development and quality of heteroepitaxy, film morphology, and electrical transport) on such key deposition parameters such as the growth temperatures of the insulating AlN buffer layer and the InN overlayer and their thicknesses have been determined. Three prominent effects of the AlN buffer layer are (1) the stabilization of heteroepitaxial growth over a broad range of film and buffer layer growth temperatures; (2) the attainment of a higher Hall mobility (up to 60 cm2/V s) over much of the same range; and, (3) the retention of heteroepitaxial growth, higher Hall mobility, and pseudo-two-dimensional growth even in the limit of an InN layer of ∼40 A(ring). In the context of a structure-zone model, the AlN buffer layer is projected to effectively raise the growth temperature of the InN thin film. The increase in effective growth temperature is, however, insufficient to overcome low atomic and cluster mobility and to achieve single-crystal InN thin film growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354822
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  • 195
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    Re-evaporation effects and optical properties of molecular-beam-epitaxial AlGaAs/GaAs/AlGaAs wells (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1697-1699 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Elemental materials that condense on surfaces near effusion cells can be reevaporated toward substrates when heated by radiation from effusion furnaces. There they accumulate as unwanted impurities at interfaces and distribute throughout epitaxial films during growth. This effect is greatly increased when shutters are closed. Re-evaporated aluminum is shown to degrade minority-carrier properties of Al0.3Ga0.7As/GaAs double heterostructures. Modified temperature schedules and hardware to reduce re-evaporation effects are suggested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354823
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  • 196
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    Measurement of thermal stress and stress relaxation in confined metal lines. I. Stresses during thermal cycling (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1716-1724 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A method based on the bending beam technique has been developed to measure the thermal stresses of fine lines confined by a dielectric layer. This method has been employed to determine the thermal stress of Al (2 at. % Cu) lines passivated by a SiO2 overlayer between room temperature and 400 °C. The effect of quartz confinement was analyzed by matching the thermal displacement at the metal/passivation interfaces and by imposing a mechanical equilibrium condition on the structure. The analysis enables us to deduce the triaxial stress components of metal and passivation from measurements of the substrate bending parallel and perpendicular to the length direction of the lines. Results of the measurements show a substantial stress enhancement as a result of the confinement, with the stress level significantly higher than that of a passivated blanket film. Parameters that influence the magnitude of the stress components are line geometry, layer deposition conditions, and the extent of plastic deformation during thermal cycling. Results of the measurements are consistent with those determined using x-ray techniques.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354826
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  • 197
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    Influence of mismatch on the defects in relaxed epitaxial InGaAs/GaAs(100) films grown by molecular beam epitaxy (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1731-1735 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thick (∼3 μm) films of InxGa1−xAs grown on GaAs(100) substrates, across the whole composition range, have been examined by transmission electron microscopy and double-crystal x-ray diffraction. The results were compared with the observed growth mode of the material determined by in situ reflection high-energy electron diffraction in the molecular beam epitaxy growth system. The quality of the material degraded noticeably for compositions up to x∼0.5 associated with an increased density of dislocations and stacking faults. In contrast, improvements in quality as x approached 1.0 were correlated with the introduction of an increasingly more regular array of edge dislocations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354827
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  • 198
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    A macroscopic model for focused-ion-beam-induced deposition (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1762-1769 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A time-dependent model for focused-ion-beam-induced deposition is presented which explicitly takes the scanning strategy of the beam during deposition into account. The model differentiates between the contribution of the beam center and that of the beam wings, and contains all major experimental variables such as current density, focus size, scan speed, and frame time. The deposition rate has been measured for tungsten as a function of the major experimental variables. The model has been fitted to these data and is found to describe the various dependences very well. By use of the model inclusive of the parameters obtained from the fit, we can predict optimum deposition conditions. Furthermore, the model clarifies effects observed during deposition on the structured surface of an integrated circuit, such as redeposition of sputtered material and poor step coverage due to an impeded gas flow.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354805
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  • 199
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    Optical absorption spectrum of hydrogenated amorphous silicon using photo-pyroelectric spectroscopy (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1799-1804 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The optical absorption coefficient α of doped and undoped hydrogenated amorphous silicon (a-Si:H) has been measured for photon energies from 2.2 to 1.0 eV using photo-pyroelectric spectroscopy (PPES). A simplified experimental setup and analysis for extracting α from the PPES data are described. In PPES the temperature rise induced in the a-Si:H thin film due to weakly absorbed light is detected via a pyroelectric polymer in thermal contact with the sample. This technique presently has a sensitivity of αd(approximately-greater-than)10−3, where d is the sample thickness.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354784
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  • 200
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    Magnetotransport and magneto-optical properties of δ-doped InSb (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1793-1798 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Results of Shubnikov–de Haas (SdH), cyclotron resonance (CR), and Hall-effect measurements on δ-doped InSb:Si films grown by molecular-beam epitaxy on insulating InP substrates are reported. The investigation covers samples with sheet densities of Si dopant atoms ranging from 1×1011 to 1×1013 cm−2, temperatures from 4.2 to 300 K, and fields from 0 to 7 T. The SdH oscillations show that the samples contain electrons of two-dimensional nature, occupying multiple subbands. The effective masses obtained from the CR data correspond well to the subband occupation densities. The Hall measurements as well as the CR experiments also give evidence for the presence of additional electrons, with the conduction-band-edge mass m*=0.014m0 of bulk InSb, which exist presumably in the bulk of the films.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354783
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