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  • Chemistry  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 18 (1992), S. 107-112 
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The dielectric function ε spectra of Si-doped n-type GaAs crystals at room temperature (296 K) have been determined between 1.53 and 5.01 eV, using variable angle spectroscopic ellipsometry (VASE). Samples with carrier concentrations ranging from 4.6 × 1017 to 3.3 × 1018 cm-3 were measured. The effects of surface microscopic roughness, native oxide overlayer and the subsurface damage were mathematically removed with an appropriate multilayer model. The GaAs dielectric function spectra were modeled using the sum of seven harmonic oscillators, whose center energies, half-widths and amplitudes were fitting parameters in the multilayer model. It was found that, as the doping level increased, the E1 and E1 + Δ1 peak structures near 3 eV in the ε2 spectrum broadened considerably more than the E0′ and E2 peak structures near 4.7 eV, while the amplitude of the E1 peak decreased with respect to that of the E1 + Δ1 peak. Other effects due to doping were a shift of the ε2 spectrum towards lower energies and a decrease in the amplitude of the E2 peak.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 18 (1992), S. 113-118 
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Samples of polycrystalline silicon (poly-Si) thin-film multilayers were prepared by low-pressure chemical vapor deposition. Analysis of these samples by cross-sectional transmission electron microscopy (XTEM) revealed large changes in grain size between the undoped-as-deposited and doped-annealed poly-Si layers. Roughness at the top of the poly-Si layers was also observed by XTEM. Non-destructive variable angle spectroscopic ellipsometry (VASE) was used to characterize these structures and to determine the layer thicknesses and compositions. The poly-Si and roughness layers were each modeled as physical mixtures, using the Bruggeman effective medium approximation, and incorporated into the appropriate multilayer fitting models. As a result, layer thicknesses and compositions, as well as the surface and interface roughnesses, were determined. The VASE-obtained thicknesses compared well with those determined by destructive XTEM. The effects on the poly-Si layer microstructure due to doping and annealing were also characterized.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Silicon oxynitride (SiOx Ny) thin films were deposited on silicon substrates by ion-assisted deposition. Variable angle spectroscopic ellipsometry (VASE) was used to optically characterize the deposited film properties, such as layer thickness and composition, film surface and interface qualities, as well as the retractive index spectrum in the wavelength range 320-820 nm. The measured VASE spectra were analyzed by assuming SiOx Ny to be a physical mixture of two distinct phases, silicon dioxide and silicon nitride, using the Bruggeman effective medium approximation. Remarkably good agreements between the measured spectra and model calculations were obtained over the entire spectral range for all the samples studied. Layer thicknesses of SiOx Ny films determined by VASE were consistent with their corresponding nominal values. The ellipsometrically deduced refractive index spectrum was observed to be strongly dependent on the film composition. In addition, the film refractive index at each applied wavelength was found to be a linear function of its constituent relative volume fraction. The results from VASE analysis also indicated that all the sample films investigated exhibited smooth surfaces, sharp interfaces between the film and substrate and high packing density.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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