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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3381-3385 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on optical absorption its magnetic circular dichroism (MCD), optically detected electron spin-resonance (ODESR), and electron nuclear double-resonance (ODENDOR) investigations of plastically deformed semi-insulating GaAs. By plastic deformation arsenic antisite defects are created which show a similar ODESR pattern as EL2 defects present in the material prior to deformation. EL2 and the new antisite defects can be distinguished by their different spectral dependence of the MCD. The new antisite defect formation starts at 2% deformation and is investigated as a function of the degree of deformation; additional EL2 defects are not created. With ODENDOR it is shown that the atomistic structure of the EL2 defects changes in the deformed GaAs.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 1454-1462 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electrical and optical properties of liquid encapsulated Czochralski grown, Ga-rich (melt composed of 55% Ga and 45% As), p-type GaAs were studied by the Hall effect, capacitance-voltage measurements, magnetic circular dichroism, optically detected electron spin resonance, deep level transient spectroscopy (DLTS), and Raman spectroscopy. Two levels with ionization energies of 78 and 203 meV above the valence band edge were examined and fitted to the singly and doubly charged ground states of a double acceptor which is designated an EK2 center. The Raman scattering cross sections for electronic excitations were determined from the defect concentrations measured by DLTS. The EK2 center is electrically passivated via a remote microwave hydrogen plasma technique. It can be reactivated by heat treatments with an activation energy of Ea=1.4 eV. The concentrations of the two levels were equal to each other in four as-grown samples, in samples following passivation, and at all stages during the subsequent reactivation. The observations are inconsistent with previous suggestions that the levels are due to two separate defects.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 7533-7542 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Microwave detection of the Shubnikov–de Haas (SdH) effect as a contact-free characterization technique for different types of two-dimensional semiconductor structures is explored in the low magnetic field region. The detection technique and the data analysis are described. The character and relevance of the single-particle relaxation time that can be detected by this technique are distinguished from the usual transport scattering time. The measured values of the carrier concentration and single-particle relaxation time agree with electrical measurements, while the problem of making contacts on the structure is avoided. Uncertainties in the analysis for the single-particle relaxation time are discussed. Cyclotron resonance, optically detected cyclotron resonance, and magneto-photoluminescence are applied as other contact-free techniques on the same samples. The results and suitability of these techniques are compared with the microwave detection of the SdH effect.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 4523-4526 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Cd1−xZnxTe crystals grown by the traveling heater method have been investigated by low-temperature photoluminescence. The excitonic energy gap as a function of the alloy composition was determined over the complete range of x=0 to x=1. The composition dependent broadening of the neutral acceptor bound exciton (A 0X) line was determined. Theoretical calculations, where the A 0X exciton is treated within the pseudodonor model and the conduction/valence band offset between CdTe and ZnTe is taken into account, give close agreement with the experiment for x≤0.77. Evidence for clustering of Zn atoms is found for x≥0.77.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 7253-7259 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Proteins change their global conformation very slowly compared to the time scales of most localized internal motion. The relationship between these slow and fast processes was investigated with the aid of a stochastic model recently applied to a related problem of protein folding [Zwanzig et al., Proc. Natl. Acad. Sci. 89, 20 (1992)]. In the present study a change in conformation was treated as a bond rotational isomerization that may only occur when several other gating bonds simultaneously assume permissive orientations. The requirement of correct orientation of these gating bonds is analogous to the alignment of the tumblers in a lock. For a range of reasonable choices of parameters, this model generated realistic time scales for protein conformational changes. Although the transition time depended on the value of an energy bias against the permissive position of a gating bond, the model could still generate reasonable transition times in the absence of an energy bias. For a wide range of parameters chosen to give typical experimental rates for biological transitions, the model predicted conformational changes with simple exponential kinetics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 931-933 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Shubnikov–de Haas oscillations in 150 A(ring) single quantum wells of In0.53Ga0.47As/InP are detected without contacts, using a conventional electron paramagnetic resonance (EPR) spectrometer. The two-dimensional properties of the signal are verified and the carrier concentration is deduced from the period of the oscillations. The effective mass m* = 0.041mo obtained from the temperature dependence of the amplitude of the oscillations confirms that the signal originates from the In0.53Ga0.47As quantum well.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 1857-1859 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electrically detected magnetic resonance experiments showing spin dependent recombination in commercial p-n diodes are presented. The observed anisotropy in the g values along with the marked shift from the free electron g-value point to a metal-vacancy complex. Deep level transient spectroscopy reveals the presence of the Pt acceptor level (0/−) at Ec−0.23 eV and the donor level (+/0) at Ev+0.32 eV in the same device. Calculations of the recombination rates support that spin dependent recombination occurs at the Pt (+/0) donor level.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 1033-1035 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the structural and optical properties of GaN epitaxial layers grown on 6H-SiC. We employed the sublimation sandwich method to grow single crystal layers at high growth rates with free carrier concentrations of 2×1017 cm−3. Very narrow x-ray diffraction peaks of the GaN (0002) plane are obtained indicating the high quality of this system. These findings are directly reflected in the optical properties. The photoluminescence shows a single sharp exciton line with a half width of 4 meV. Impurity related donor acceptor transitions are seen with very weak intensities. However, at lower energies the internal luminescence transitions of the 3d transition metal ions Fe and V are observed.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 2120-2122 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The defect properties of as-etched and annealed porous silicon are studied by electron paramagnetic resonance (EPR) and optically detected magnetic resonance (ODMR). The paramagnetic defect observed is closely related to the Pb0 center at the Si/SiO2 interface. In EPR a minimum defect density of 1016 cm−3 is observed for the as-etched silicon, which reaches a maximum of 8×1018 cm−3 for samples annealed at about 400 °C. In the ODMR experiments, the same dangling bond center is observed on the 1.5 eV luminescence band enhancing the luminescence—but with increased sensitivity and as a decrease of the emission intensity in the infrared emission band at 1 eV of porous silicon.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 2911-2913 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The iron acceptor, FeZn, in as-grown ZnTe has been investigated by electron-paramagnetic resonance (EPR) and by photo-EPR. The photo-EPR investigation shows that the Fe+ EPR signal is enhanced by optical illumination, and the threshold energy for enhancement, at ≈1.75 eV, suggests that the acceptor level is located at 0.65 eV below the conduction band. The energy dependence of the optical cross-section for hole ionization, σp0, was determined from an analysis of the time dependent EPR signals. This first determination of the Fe+ acceptor energy level in a II-VI semiconductor allows us to predict the positions of the acceptor level in other II-VI materials. In particular, for Cd-based II-VI materials it is suggested that the acceptor level of iron is located degenerate with the conduction band.
    Type of Medium: Electronic Resource
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