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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 4003-4010 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In previous papers, a new model was proposed for the optical dielectric function of zinc blende semiconductors and was applied successfully to the alloy series AlxGa1−xAs. It was found to be more generally valid than any previous model. In this paper, it is used to obtain an analytic expression for the dielectric function of the II-VI compound CdTe at room temperature. Unlike the previous application, additional polynomial terms in the real part of the optical dielectric function are not introduced, so that the Kramers-Kronig relationship between the real and imaginary parts of the dielectric function is satisfied exactly. As demonstrated before, the model covers not only the entire photon energy range of the given spectral data, but also is valid below and somewhat above the given spectral range. This is advantageous especially when spectral data are not provided in the range of interest, or when joining two separate data causes an artificial discontinuity. The model determines the optical dielectric function in the limit as the line broadening approaches zero, which is useful in calculating the optical dielectric function at all temperatures. For demonstration, the optical dielectric function at 70 K and 600 K is calculated and presented. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 2958-2966 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Spectroscopic ellipsometry using photoelastic modulator [phase modulated spectroscopic ellipsometry (PMSE)] has been improved in the spectral range. Spectroscopic ellipsometry using the rotating analyzer [rotating analyzer spectroscopic ellipsometry (RASE)] has demonstrated its capability of measuring the reflectivity ratio, ρ(ω), from 1.5 to 6 eV with a single scan, but PMSE has not been able to do so. We demonstrate that PMSE also can measure ρ(ω) from 1.5 to 6 eV with a single scan. We discuss the problems and show their solutions to achieve this goal. We also discuss the accuracy of our PMSE by comparing the spectral data by RASE with those by our PMSE. We find that the simplest possible procedure with our system provides reasonably accurate values, after including the zone average which is easy to perform with our system. The extension of the spectral range is a decisive advantage, especially in studying the E1 structure of the wide band gap materials such as ZnSe.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 992-997 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Substantial improvements have been made in the sensitivity of an ac susceptibility measurement system which determines the pressure dependence of the superconducting transition temperature, Tc(P). The pressure, P, is determined near Tc from the position of the R1 and R2 fluorescence peaks from ruby chips. The system was used to determine Tc(P) for several high Tc single crystals, but was not sufficiently sensitive to determine Tc(P) of polycrystalline samples for HgBa2CuO4+δ. This motivated us to improve the sensitivity of our system. Other parts of the system and the data analysis procedures also have been improved. As a demonstration, Tc(P) of HgBa2CuO4+δ polycrystal to 4 GPa is presented. The improvement of the system using the diamond anvil cell opens the possibility of measuring Tc above 10 GPa and on smaller samples.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Physics and chemistry of minerals 22 (1995), S. 137-144 
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract The normal modes of vibration and their frequencies are calculated for dioptase, a mineral whose crystal structure (space group R $$\bar 3$$ or C 3i 2 ) consists of puckered six-membered silicate rings (Si6O18) linked by Cu2+ ions and H2O groups. The calculation employs a valence force potential consisting of central interactions between nearest neighbors and bond-bending interactions centered at the Si4+ and Cu2+ ions. The force constants are determined by fitting the calculated frequencies to values obtained by measuring the single-crystal Raman spectra. The calculated frequencies are in reasonable agreement with experiment, permitting assignment of normal modes to the observed spectral frequencies. Considerable mixing of Cu and H2O motions with those of the ring is found for the Raman-active modes below 430 cm-1. The normal modes and frequencies of the hypothetical isolated ring with C 3i symmetry are determined by neglecting all interactions between the rings and the surrounding Cu and H2O. The identification of normal modes characteristic of the puckered six-membered silicate rings and the effect of the environment on these modes may prove useful in the interpretation of the Raman spectra of amorphous silicates.
    Type of Medium: Electronic Resource
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