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  • 1
    Electronic Resource
    Electronic Resource
    Depletion mode optoelectronic modulation spectroscopy (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 6943-6953 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The depletion mode of opto-electronic modulation spectroscopy (OEMS), spectroscopically senses the electrical response to wavelength modulated monochromatic illumination as trap states in the depletion region of a semiconductor device are cyclically excited. The method is demonstrated using metal–Si3N4–GaAs field-effect transistors in which the charge in the gate depletion region is detected through its effect on the channel current. The optical transition energies of trap levels were revealed and the charge exchange mechanisms identified unambiguously by examining the phase of the detected signal with reference to the phase of the photon energy variation. In-phase responses originate from electron trap states while responses of opposite sign derive from hole traps. Many of the states corresponded closely in energy with ones previously reported in vapor-phase-epitaxy GaAs materials. Charge exchange with energetically discrete and continuously distributed traps is theoretically described when they are excited by photons having periodic energy modulation. The results indicate that the magnitude and phase of the OEMS response spectra are determined by the relative thermal and optical emission rates of trapped charges. Deep level transient spectroscopy (DLTS) measurements made on the same samples could not reveal the responses of bulk levels that the OEMS technique showed were present; this was because the DLTS spectra were dominated by the interface continuum response. This illustrates clearly an important advantage of the technique. The method is equally applicable to other devices in which a space-charge region regulates the channel current. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363743
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  • 2
    Electronic Resource
    Electronic Resource
    Ferromagnetic resonance of sputtered Co/Mn multilayers (abstract) : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 6266-6266 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Co/Mn multilayers were prepared by rf sputtering onto single-crystal MgO and sapphire substrates resulting in, respectively, (001)- and (111)-oriented layers. The structure was thoroughly analyzed by x-ray scattering in various geometries (Q. Wang et al. to be published). For the magnetic investigations, ferromagnetic resonance (FMR) was applied. Complementary measurements employed the magneto-optical Kerr-effect (MOKE) and Faraday balance magnetometry. Results for the in-plane anisotropy, the surface anisotropy, the magnetization, and the FMR linewidth are presented. The comparison with other Co-based multilayer systems indicates that both the structural and the magnetic properties of the Co/Mn system are more complicated than in the case of systems with a presumably weaker electronic interaction at the interface [see also K. Ounadjela et al., Phys. Rev. B 49, 8561 (1994)]. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362030
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  • 3
    Electronic Resource
    Electronic Resource
    59Co and 55Mn NMR of CoMn alloys and multilayers : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 6300-6302 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 59Co and 55Mn NMR measurements have been made on a range of CoMn materials: dilute powder alloy, thin-film alloys, and multilayers. Our results suggest that in dilute alloys isolated atoms of Mn couple both ferro and antiferromagnetically to the Co host, with the latter producing a reduction in the magnitude of the Co hyperfine field of 17%. This reduction of hyperfine field appears similar for both the fcc and hcp phases of Co. NMR on Co/Mn sputtered multilayers shows large changes in the hyperfine field distribution between a film with Mn layers of 10 A(ring) and Mn layers of 30 A(ring). © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362044
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  • 4
    Electronic Resource
    Electronic Resource
    The effect of plasma pretreatments on interface state electron emission in Si3N4–GaAs structures (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 5793-5801 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The static and dynamic properties of interface states between silicon nitride and n-GaAs have been studied. Comparisons have been made between interfaces that were untreated and ones which were plasma pretreated with Ar, N2, H2, and NH3. With the exception of hydrogen the pretreatments did not significantly alter the quiescent surface Fermi level position or the shape of the interface state distribution in the metal-insulator-semiconductor field effect transistor test structures. In all of the samples it required about 10 μs to complete the transfer of the induced charge from the bulk edge of the depletion region to the interface. Charge which had reached the interface equilibrated there within 100 ns. This charge gave rise to a relatively slow emission transient and had a thermal emission energy consistent with emission from the surface Fermi energy to the lower edge of an interface state band, in accord with the interface state band model. The extent in energy of this band depended on the surface treatment. The insensitivity of the emission time constant to both filling time and insulator electric field suggests that irrespective of the treatment the equilibrated charge remained at the interface and did not tunnel into the insulator. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359594
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  • 5
    Electronic Resource
    Electronic Resource
    Ferromagnetic resonance of sputtered Co/Mn multilayers : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 4929-4931 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Co/Mn multilayers were prepared by rf sputtering onto single-crystal MgO(001) and Al2O3(112¯0) substrates resulting in, respectively, (001)and (111)-oriented layers. The structure was thoroughly analyzed by x-ray scattering in various geometries. For the magnetic investigations, ferromagnetic resonance (FMR) was applied. Complementary measurements employed the magneto-optical Kerr effect and Faraday balance magnetometry. Results for the in-plane anisotropy, the surface anisotropy, the magnetization, and the FMR linewidth are presented. The comparison with other Co-based multilayer system indicates that both the structural and the magnetic properties of the Co/Mn system are more complicated than in the case of systems with a presumably weaker electronic interaction at the interface. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361591
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  • 6
    Electronic Resource
    Electronic Resource
    Structural and magnetic properties of Co/face-centered-cubic Mn(001) multilayers (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 1689-1695 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The structural and magnetic properties of Mn in Co/Mn (001) multilayers were investigated by x-ray scattering, by magneto-optical Kerr effect measurements, and with a Faraday balance. The multilayers were deposited by rf-sputtering on MgO(001) substrates. Small angle x-ray reflectivity scans and high angle Bragg scattering confirmed good layer quality and crystal coherence properties. In- and out-of-plane x-ray scattering revealed a coherent growth of face-centered-cubic (fcc) (or fct) Mn on fcc Co(001). The stability limit of the metastable fct Mn structure is about 20 A(ring) or 10 atomic layers. The magnetic exchange coupling appears to be partly antiferromagnetic with a first maximum located between 20 and 30 A(ring). Saturation magnetization measurements indicate no ferromagnetic moment for the fct Mn layers. Furthermore, the saturation moment per unit volume is reduced as compared to the bulk Co value, suggesting the presence of "dead layers'' at the Co/Mn interfaces. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360266
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  • 7
    Electronic Resource
    Electronic Resource
    Structural and magnetic studies of FexCo1−x(001) alloy films on MgO(001) substrates (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 1055-1060 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin epitaxial FexCo1−x alloy films sputtered on MgO(001) substrates were studied by x-ray scattering and by the magneto-optical Kerr effect in order to investigate the structural phase stability induced by the substrate and to relate the magnetic properties to the alloy film structure. Alloy films with a thickness of about 20 nm and concentrations from x=1 to x=0.3 exhibit a bcc (001) growth with the in-plane [100] axis parallel to the MgO[110] axis. For pure Co (x=0) a fcc (001) structure with the Co[100] axis parallel to the MgO[100] axis was obtained. For x=0.15 no out-of-plane or in-plane Bragg peak could be observed, possibly due to the bcc-fcc structural phase transition. Kerr rotation angles in saturation as a function of x reveal a shape similar to the Slater–Pauling curve. Magnetic hysteresis measurements reveal a fourfold anisotropy with easy axes parallel to the FexCo1−x[100] crystal axis for 1≥x≥0.8, and parallel to the FexCo1−x[110] crystal axis for 0.7≥x≥0.3. In pure Co the easy axis lies parallel to the fcc-Co[110] crystal axis. Finally, for x=0.28 a step in the magnetic hysteresis in the FexCo1−x[11¯0] direction indicates an overlap of a fourfold and twofold magnetic anisotropy. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358965
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  • 8
    Electronic Resource
    Electronic Resource
    Commissioning and operation of the beamline for photoelectron spectroscopy in NSRL : Proceedings of the 5th international conference on synchrotron radiation instrumentation (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 1830-1832 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A grazing incidence spherical grating monochromator (SGM) for photoelectron spectroscopy has been set up in NSRL. It covers the energy range 10–1000 eV. The primary results of commissioning and operation of the beamline have been described. The resolution power could be obtained from 500 to 1000 (E/ΔE) with 50 μm of slit opening in a wide range of photon energy. The improvement of the beamline performance is continuing. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145796
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  • 9
    Electronic Resource
    Electronic Resource
    Quantum transport in high mobility modulation doped Ga0.25In0.75As/InP quantum wells (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 2112-2122 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on edge state transport in a ternary material, a modulation-doped InP/Ga0.25In0.75As/InP quantum well, where the electron transport takes place in the highly strained Ga0.25In0.75As layer. The electron mobility is, even though fundamentally limited by alloy-disorder scattering, determined by the two-dimensional electron concentration. By varying the distance between the modulation-doped layer and the two-dimensional electron gas we influence the single particle relaxation time but not the electron mobility. Special attention is paid to the effect of dislocation formation in the conducting Ga0.25In0.75As layer. In addition to the quantum Hall and the Shubnikov–de Haas effect a strong, nonlocal transport behavior, which is maintained after illumination, is observed. This effect is explained by the low defect density and the Fermi level pinning on the etched Ga0.25In0.75As surface, at an energy close to the same as the Fermi energy of the two-dimensional electron gas. Furthermore, overshoot effects of the quantum Hall plateaus introduced by the high and varying effective (many-body) g value are investigated. The g value is further addressed in an experiment on a wet etched quantum wire in which values enhanced up to around 45 were found. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.368272
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  • 10
    Electronic Resource
    Electronic Resource
    Theoretical investigation on quantum well lasers with extremely low vertical beam divergence and low threshold current (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 8-14 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A specially designed quantum well laser for achieving extremely low vertical beam divergence was reported and theoretically investigated. The laser structure was characterized by two low index layers inserted between the waveguide layers and the cladding layers. The additional layers were intended to achieve wide optical spread in the cladding layers and strong confinement in the active region. This enabled significant reduction of beam divergence with no sacrifice in threshold current density. The numerical results showed that lasers with extremely low vertical beam divergence from 20° down to 11° and threshold current density of less than 131 A/cm2 can be easily achieved by optimization of the structure parameters. Influences of individual key structure parameters on beam divergence and threshold current density are analyzed. Attention is also paid to the minimum cladding layer thicknesses needed to maintain low threshold current densities and low internal loss. The near and far field patterns are given and discussed. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.366727
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