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  • 1
    Electronic Resource
    Electronic Resource
    Electron-energy-loss spectroscopy of Fe thin films on GaAs(001) : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 6501-6503 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An electron-microscopy-based technique of electron-energy-loss spectroscopy (EELS) has been used to characterize electronic and magnetic properties of ultrathin Fe films grown on GaAs(100) surface, as a function of the film thickness. Large-area electron transparent membranes for microscopic analysis are prepared by ion-beam thinning or chemical etching from the substrate side, and the top surface of the ultrathin Fe film is protected by a thin Cr layer. Analysis of the Fe 2p, Cr 2p, and O 1s absorption spectra confirms that only the Cr layer is oxidized. The local magnetic moments of the ultrathin Fe films are deduced from the "white line'' branching ratio in the Fe 2p absorption spectra. For Fe films as thin as 150 A(ring), the magnetic moment is not different from that found in bulk α-Fe. For a 70-A(ring) Fe film, the local magnetic moment is enhanced although the average magnetization is reduced. As doping is suspected to be the cause for the departure from bulk α-Fe properties. In the case where the 50-A(ring) film is polycrystalline and discontinuous, spatially resolved EELS has been used to distinguish small island clusters from large crystalline particles. The large particles are α-Fe crystallites and the islands are probably also heavily affected by As doping.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356950
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  • 2
    Electronic Resource
    Electronic Resource
    Reflection of plane waves at medium–composite interfaces and input acoustic impedance of laminated piezoceramic polymer composites (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 5503-5505 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Plane wave propagation at the composite–medium interface is analyzed for the piezoceramic polymer composites with laminated periodic structure. It is found that the input acoustic impedance of the composite depends on the elastic properties of the medium at the interface and in general is a complex number and dispersive. It is also found that the reflected wave from the medium–composite interface suffers a more than 180° phase change, which implies that the thickness of the conventional antireflection "quarter wave matching layer'' at the interface should be less than a quarter wave length. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362741
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  • 3
    Electronic Resource
    Electronic Resource
    Quantum dynamics of chirped excitation of multimode systems (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 3823-3834 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We investigate the effectiveness of chirped laser pulses in exciting a multimode system, where a vibrational mode is coupled to a large number of bath modes. We solve the Liouville equation for this model numerically to investigate the roles played by laser frequency, laser intensity, pulse width, frequency sweeping rate, and bath relaxation times in inducing vibrational excitation. We investigate the range of parameters for which chirping excitation is efficient for multimode systems. In addition, we study constant-frequency excitations using the present model, revealing the special effects of phase relaxation time and the phenomenon of molecular bistability. Furthermore, we present results on quantum decoherence and assess the validity of an effective Hamiltonian method. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.478271
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  • 4
    Electronic Resource
    Electronic Resource
    Organometallic growth and characterization of GaxIn1−xP (x=0.51, 0.65, 0.69) (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 1346-1351 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The growth and characterization of GaxIn1−xP (x=0.51, 0.65, 0.69) are described in this paper. The organometallic vapor-phase epitaxial (OMVPE) growth was carried out in an atomospheric pressure reactor using trimethylgallium (TMGa), trimethylindium (TMIn), and phosphine (PH3). GaAs and commercially available hydride vapor-phase epitaxial GaAs0.70P0.30 and GaAs0.61P0.39 were used as the substrates. The influence of growth temperature and V/III ratio on the properties of the OMVPE epilayers was studied. This resulted in the determination of an optimum growth temperature of 625 °C and an optimum V/III ratio range of 40–50. The results of the mismatch due to the different lattice constants of the GaxIn1−xP epilayer and the substrate were investigated. It was found that high-quality GaxIn1−xP epilayers can be obtained only when the mismatch ||Δa/a0|| is less than 1×10−3. Under the conditions mentioned above, epilayers were reproducibly obtained with featureless surface morphologies, and photoluminescence (PL) with high intensities and narrow half-widths (41–43 meV at 300 K). The dislocation etch pit densities ρ of Ga0.65In0.35P and Ga0.69In0.31P epilayers were 7.4–8.6×104 cm−2, grown lattice matched to GaAs1−yPy ( y=0.30, 0.39) substrates with ρ=6.4–7.5×105 cm−2. The degradation of PL intensity after annealing at temperatures between 400 and 600 °C in H2 or N2 indicates an increase in the surface recombination velocity for GaInP epilayers. Etching 30 A(ring) from the surface was found to restore the original PL intensity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.337308
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  • 5
    Electronic Resource
    Electronic Resource
    A physics-based bipolar transistor model for low-temperature circuit simulation (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 4474-4480 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A comprehensive bipolar transistor model based on the Gummel–Poon model [Bell Syst. Tech. J. 49, 827 (1970)] for low-temperature circuit simulation is presented. Relevant low-temperature physics such as doping-dependent dielectric permittivity, temperature-dependent free-carrier mobility and intrinsic carrier density, and de-ionization of impurity dopants are included in the model. Consequently, the model does not require temperature fitting parameters as does the Gummel–Poon model. Comparisons of the present model with the Gummel–Poon model, with experimental data, and with simulation from a two-dimensional device simulator (pisces) are included.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343945
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  • 6
    Electronic Resource
    Electronic Resource
    Doping studies of Ga0.5In0.5P organometallic vapor-phase epitaxy (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 59 (1986), S. 395-398 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Undoped Ga0.5In0.5P has been successfully grown by organometallic vapor-phase epitaxy on GaAs substrates with a free-electron concentration of 1016 cm−3 and a mobility of 1050 cm2/V s in nominally undoped material. The distribution coefficient of indium in the growth of Ga0.5In0.5P is nearly to unity. Both n- and p-type carrier concentrations of up to 1019 cm−3 have been obtained in the present study. Diethyltelluride and silane are used as n-type dopants. Dimethylzinc is used as the p-type dopant. Te is a very efficient dopant with a distribution coefficient kTe=54. The photoluminescence (PL) intensity increases with Te doping level to a maximum at n=2×1018 cm−3. The silicon distribution coefficient is temperature dependent, due to the incomplete pyrolysis of silane at the growth temperature. Si-doped Ga0.5In0.5P has a lower PL efficiency than Te-doped samples and is not strongly correlated with carrier concentration. The incorporation efficiency of Zn is low, with kZn =3.8×10−3, due to the high vapor pressure of Zn at the growth temperature. The PL intensity of Zn-doped Ga0.5In0.5P also increases with Zn doping level to a maximum at p=2×1018 cm−3 and is comparable to the optimum Te-doped n-type Ga0.5In0.5P. Only a single band-edge PL peak is observed in all cases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.336642
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  • 7
    Electronic Resource
    Electronic Resource
    Organometallic vapor phase epitaxial growth of AlGaInP (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 1380-1383 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: AlxGayIn1−x−yP with x+y=0.51, lattice matched to the GaAs substrate, has been grown by organometallic vapor phase epitaxy. The simple, horizontal, IR heated system operates at atmospheric pressure using the reactants TMAl, TMGa, TMIn, PH3, and H2. Alloys giving room temperature, band edge photoluminescence (PL) have been grown in the temperature range 625–780 °C. Emission wavelengths as short as 5820 A(ring) (2.13 eV) are reported. High growth temperatures are found to give layers with the best surface morphology and PL intensity. The use of high temperatures is especially important for high Al content alloys. PL at x=0.2 is obtained only for temperatures above 740 °C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.334491
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  • 8
    Electronic Resource
    Electronic Resource
    Visible electroluminescence from native SiO2 on n-type Si substrates (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 2358-2360 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Visible electroluminescence (EL) has been observed from Ag (film or paste)/native SiO2/n-type Si structures. The diodes show good rectification behavior and the EL occurs only under reverse bias conditions when the top Ag electrode is negative. For p-type samples, a forward bias is required. The intensity of the EL is proportional to the diode current and its spectrum peaks at 620–640 nm. A model based on oxygen-related luminescent centers in the native oxide is proposed. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371056
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  • 9
    Electronic Resource
    Electronic Resource
    Effects of using the more accurate intrinsic concentration on bipolar transistor modeling (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 5911-5912 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A more accurate intrinsic concentration was suggested recently. Discrepancies between using the conventional and the more accurate intrinsic concentrations on bipolar transistor modeling are assessed in this study. Our calculations show that the conventional intrinsic concentration overestimates the collector and base currents by a factor of 1.5 to 2 but affects less severely the steady-state current gain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346942
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  • 10
    Electronic Resource
    Electronic Resource
    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 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354698
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