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  • 1
    Electronic Resource
    Electronic Resource
    Evidence of point defect supersaturation during Zn diffusion in InP single crystals (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 2843-2845 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Formation of defects during Zn diffusion into undoped and semi-insulating Fe-doped InP single crystals at 700 °C was observed by transmission electron microscopy for various diffusion conditions. Agglomerates of predominantly perfect interstitial-type dislocation loops, dislocations, and small indium precipitates inside voids are observed in the Zn-diffused crystal region. In addition, large planar arrays of precipitates are formed by climbing dislocations. From these observations it is concluded that the incorporation of Zn on In sublattice sites creates a supersaturation of In self-interstitials which is relieved by dislocation loop formation leading to a supersaturation of P vacancies and void formation. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358698
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  • 2
    Electronic Resource
    Electronic Resource
    Microwave spectra of the Ne–N2 Van der Waals complex: Experiment and theory (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 5420-5432 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: High-resolution microwave spectra of the ground state 20Ne–14N2, 20Ne–15N2, 22Ne–14N2, and 22Ne–15N2 Van der Waals complexes, involving rotational levels up to J=4, are reported. Interpretation and assignment of the observed transitions were made by combining results of measurements and theoretical predictions of the MW line positions in terms of available empirical potential energy surfaces and of a new high-level ab initio potential energy surface. The deviations of the calculated MW spectra from those observed experimentally are more uniform for the ab initio potential surface than they are for the empirical potential surfaces, allowing for reduction of the deviations to within 0.07% for all isotopomers by a single-parameter scaling of the ab initio potential energy surface. The scaled Ne–N2 interaction potential was used to predict the MW line positions for the transitions J′-J″=3-2, 4-3 for all species. A simple procedure is proposed to improve the ab initio results for atom–diatom systems on the basis of atom–atom interaction components. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.477160
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  • 3
    Electronic Resource
    Electronic Resource
    Temperature and energy dependence of ion-beam synthesis of epitaxial Si/CoSi2/Si heterostructures (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3001-3008 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The formation of buried CoSi2 layers by high-dose Co+ implantation into Si depends sensitively on the implantation temperature. Continuous buried epitaxial layers are only obtained at implantation temperatures above ∼300 °C. At temperatures below ∼200 °C, the implanted Si amorphizes, and the Co profile appears shifted towards the surface by about 250 A(ring) compared to implantations performed above 300 °C, such that no buried layers are formed. A larger sputtering yield of the amorphous than the crystalline Si and a larger mean projected range of the implanted Co+ ions in single-crystalline Si seem to be responsible for the observed shift. For sputtering yields of 100- and 200-keV Co+ ions, we obtained values of Y=2.0±0.1 at room temperature and Y=1.7±0.1 at 350 °C. Implantations with energies ≤50 keV in (100) Si and subsequent annealing yield CoSi2 precipitates or layers at the surface, but not buried layers. The growth of rhombohedral precipitates in (100)Si aggravates the formation of very thin buried silicides. The minimum thickness of buried epitaxial silicides in (100)Si produced by high-dose implantations seems to be ∼400 A(ring), which is significantly larger than the minimum thickness in (111)Si (∼200 A(ring)). Rapid thermal annealing leads to lower specific electrical resistivity values (13 μΩ cm) than conventional furnace annealing. Rutherford backscattering, He+-ion channeling, transmission electron microscopy, and sheet resistivity measurements were employed to characterize the implanted samples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346438
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  • 4
    Electronic Resource
    Electronic Resource
    Disordering in 69GaAs/71GaAs isotope superlattice structures (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 5206-5212 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Undoped 69GaAs/71GaAs isotope superlattice structures grown by molecular beam epitaxy on n-type GaAs substrates, doped by Si to ∼3×1018 cm−3, have been used to study Ga self-diffusion in GaAs by disordering reactions. In the temperature range of 850–960 °C, the secondary ion mass spectrometry (SIMS) measured Ga self-diffusivity values showed an activation enthalpy of 4 eV, and are larger than previously compiled Ga self-diffusivity and Al-Ga interdiffusivity values obtained under thermal equilibrium and intrinsic conditions, which are characterized by a 6 eV activation enthalpy. Characterizations by SIMS, capacitance-voltage (C-V), and transmission electron microscopy showed that the as-grown superlattice layers were intrinsic which turned into p type with hole concentrations of ∼2×1017 cm−3 after annealing, because the layers contain carbon. Dislocations of a density of ∼106–107 cm−2 were also present. However, the factor responsible for the presently observed larger Ga self-diffusivity values appears to be Si out-diffusion from the substrate, which was determined using C-V measurements. Out-diffusion of Si decreases the electron concentration in the substrate which causes the release of Ga vacancies into the superlattice layers where they become supersaturated. This Ga vacancy supersaturation leads to enhanced Ga self-diffusion in the superlattice layers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352002
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  • 5
    Electronic Resource
    Electronic Resource
    Formation of void/Ga-precipitate pairs during Zn diffusion into GaAs: The competition of two thermodynamic driving forces (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 4409-4422 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An experiment of diffusing Zn into GaAs has been conducted at 900 °C using Zn metal as the source material in a quartz ampoule, with or without As being included. For cases without further including As in the ampoule, the Zn profile is box shaped and the Zn-diffused region contains dislocations and void/Ga-precipitate pairs, with the void to precipitate volume ratio being essentially constant throughout the Zn-diffused region. For cases including As in the ampoule, the Zn profile is of the kink-and-tail type with the Zn-diffused region containing dislocations and void/Ga-precipitate pairs. In the profile tail region, the Ga-precipitate to void volume ratio is substantial, while in the profile kink region of high Zn concentration near the surface only voids are left. The results are interpreted in accordance with Zn and diffusion-ambient-induced Ga-As-Zn ternary alloy system thermal equilibrium requirements in general, and the consequential solid phase composition variations in particular. Without As inclusion in the ampoule, the overall Ga-As material Ga concentration in the Zn-diffused region has exceeded the allowed limit of the GaAs crystal, with the crystal composition at a limit. With the inclusion of As in the ampoule, the GaAs crystal composition in the high Zn concentration region near the surface has reached an allowed As concentration limit, but in the profile tail region the overall Ga-As material Ga concentration has exceeded an allowed limit of the GaAs crystal. This is because the vapor phase Zn and As species constitute two conflicting thermodynamic driving forces for producing GaAs crystals with two opposite and extreme compositions: As for producing As-rich crystals, and Zn for producing Ga-rich materials. The common assumption that the inclusion of As in the diffusion ampoule will ensure the whole GaAs crystal essentially at an As-rich composition does not hold during high-concentration Zn indiffusion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354412
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  • 6
    Electronic Resource
    Electronic Resource
    Interface structure and Schottky barrier height of buried CoSi2/Si(001) layers (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 3846-3854 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The atomic interface structure of implanted buried layers in (100) oriented Si substrates has been characterized by quantitative high-resolution transmission electron microscopy on cross-section specimens. The buried layers were produced by high-dose Co+ ion implantation [100 and 200 keV Co+ ions, (1–2)×1017 cm−2] at 350 °C and subsequent rapid thermal annealing at 750 and at 1150 °C. Planar interface regions of high perfection with domains of different atomic interface structures, and interface steps, frequently with {111} facets, were observed. Comparison with computer-simulated images for various interface models yields evidence for interface regions with six-fold and eight-fold coordination of the Co interface atoms. Furthermore, regions with interfaces showing a continuous transition as well as Co-rich interfaces were found. Measurements of the Schottky barrier heights have been performed and show smaller values for the upper CoSi2/n-Si(001) interfaces than for the lower ones. Possible correlations between the interface structures and the resulting electronic properties are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354479
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  • 7
    Electronic Resource
    Electronic Resource
    Optimization of modulation-doped Ga1−xInxAs/InP heterostructures towards extremely high mobilities (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 4489-4493 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This paper presents a study of the electrical and structural properties of inverted modulation-doped GaInAs/InP heterostructures grown by low-pressure metalorganic vapor phase epitaxy. First, the thickness of the GaInAs layer was optimized in lattice-matched samples to find the smallest thickness in which high Hall mobility is observed. Next, in a section closest to the InP the In content was varied. A steady increase of mobility with indium composition was observed. A maximum of 450 000 and 15 500 cm2/V s was obtained for a 10-nm-thick Ga1−xInxAs layer with x=0.77 at 6 and 300 K, respectively. Channels with higher indium content exceed the critical thickness and mobility drops off sharply. The decreasing mobility correlates with the formation of misfit dislocations at the interface indicating increasing scattering processes of the GaInAs layer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352789
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  • 8
    Electronic Resource
    Electronic Resource
    The microwave rotational spectrum of the Ar–CO dimer (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 9399-9404 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Pure rotational spectra of four different isotopomers of the dimer Ar–CO have been investigated between 8 and 18 GHz using a pulsed beam cavity Fourier transform spectrometer. The spectra confirm that the complex is a prolate near-symmetric rotor with an essentially T-shaped structure, and that it undergoes large amplitude zero-point motion. It is shown that on the average the argon is closer to the oxygen than to the carbon. The transitions measured obey a-type selection rules with ΔJ=+1, ΔKa=0, and ΔKc=+1. For 40Ar–12C16O, transitions have been observed for Ka=0 and 1 with lower state J values of 1, 2, and 3. For 40Ar–13C16O and 40Ar–13C18O, a similar series was measured, but only for Ka=0. For 40Ar–13C17O, the 17O quadrupole hyperfine pattern was resolved in the rotational transition JKaKc = 202–101. Determinations have been made for rotational and centrifugal distortion constants, as well as for the 17O quadrupole coupling constant χaa. Effective values have been obtained for the length of the line from the center of mass of the CO subunit to the argon nucleus, and for the angle between this line and the CO bond.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.464371
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  • 9
    Electronic Resource
    Electronic Resource
    Optical and structural investigation of SiGe/Si quantum wells (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 2183-2185 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this letter we report photoluminescence and structural results obtained on asymmetrically strained Si0.7Ge0.3/Si single and multiple quantum wells epitaxially grown by low pressure chemical vapor deposition. Well-resolved peaks were obtained which can be attributed to quantum well excitons and their transversal optical phonon replica. A good correlation between peak properties and structure results was found. From the photoluminescence peak energies a valence band offset of 0.27 eV and an effective hole mass of 0.25 were estimated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.107073
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  • 10
    Electronic Resource
    Electronic Resource
    Damage and lattice strain in ion-irradiated AlAs (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 421-423 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Radiation-induced damage and strain in AlAs were investigated by measurements of the lattice parameter using x-ray diffraction. Irradiations employed MeV C, Ar, and Au ion beams at 25 or 80 K. The out-of-plane lattice parameter increased with fluence at low doses, saturated, and then decreased to nearly its original value. The in-plane lattice parameter did not change, throughout. These results were independent of the irradiation particle when scaled by damage energy. Selected samples were examined by high-resolution and conventional transmission electron microscopy. Recovery of the lattice parameter during subsequent thermal annealing was also investigated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112320
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