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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Chemistry of materials 5 (1993), S. 1474-1480 
    ISSN: 1520-5002
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Analytical chemistry 34 (1962), S. 1511-1513 
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 1526-1528 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Hydrogenated amorphous silicon (a-Si:H) p–i–n solar cell performance has been optimized using a two-step i-layer growth process. This effort has been guided by real-time spectroscopic ellipsometry (RTSE) studies of the nucleation and growth of a-Si:H films by plasma-enhanced chemical vapor deposition at 200 °C using a variable H2-dilution gas flow ratio R=[H2]/[SiH4]. RTSE studies during film growth with R〉15 reveal a transition from the amorphous to microcrystalline (a→μc) phase at a critical thickness that decreases with increasing R. From such results, the optimum two-step process was designed such that the initial stage of the i layer (∼200 Å) is deposited at much higher R than the bulk to ensure that the film remains within the amorphous side of the a→μc phase boundary, yet as close as possible to this boundary at low i-layer thicknesses. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 1057-1059 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The uncertainties inherent in the normalization of subgap photoconductivity spectra to the optical absorption spectra α(hv) in a-Si:H based films have been addressed. An analysis is presented which is based on optical transitions of constant dipole matrix element between parabolic distributions of extended states and exponential distributions of localized tail states. This analysis has been used to normalize the two sets of results accurately, as verified by photothermal deflection spectroscopy measurements, and is shown to be useful in the commonly encountered cases, in which the two spectra do not overlap over an extended region. Improved quantitative fits of α(hv), for photon energy from ∼1.5 to 2.4 eV, obtained on different a-Si:H based films indicate that the localized exponential band tail regions extend ∼60–70 meV above the optical gap. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 900-902 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A multichannel spectroscopic ellipsometer based on the rotating-compensator principle has been applied to obtain the evolution of spectra (1.5–4.0 eV) in the normalized Stokes vector of the light beam reflected from the surface of a nanocrystalline diamond film during growth. Spectra in the ellipsometry angles (ψ, Δ) provide the time evolution of the microstructure and optical properties of the film in thin layers, whereas the spectra in the degree of polarization provide the time evolution of nonuniformities in the growth process attributed to light scattering by diamond nuclei in the initial stage of growth and to thickness gradients over the probed area in thicker layers. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 1086-1088 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In situ ellipsometry provides monolayer sensitivity to the reaction of B2H6:SiH4 doping gas mixtures with p- and i-type plasma-enhanced chemical vapor deposited (PECVD) amorphous silicon (a-Si:H) surfaces at 180 and 250 °C. This low-temperature reaction, leading to the slow growth (1–3 A(ring)/min) of a-Si:H:B by CVD (without plasma excitation), requires a clean a-Si:H surface and both B2H6 and SiH4 in the doping gas. We suggest that the high B content of CVD a-Si:H:B at p-i and i-p interfaces and on the film-coated regions of single-chamber reactors, may contribute to poor interface characteristics and residual contamination in devices.
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  • 7
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The recently developed technique of real time spectroscopic ellipsometry (SE) has been applied to characterize the nucleation of diamond on c-Si by W filament-assisted chemical vapor deposition, leading to improved control over the process. Specifically, techniques are developed which minimize W contamination at the diamond/substrate interface; calibrations are performed which determine the temperature of the top ∼250 A(ring) of the substrate under growth conditions; and alterations in gas flow conditions are implemented in response to diamond growth for a reduced induction time. With these procedures in place, real time SE provides the induction time, nucleation density, and mass thickness, and is in quantitative agreement with ex situ scanning electron microscopy.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 2231-2237 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The stress in diamond films prepared by microwave plasma CVD was investigated as a function of methane concentration (0.2%–3.0%) and deposition temperature (600–900 °C). Tensile and compressive total (thermal and intrinsic) stress were observed, depending on the deposition conditions. The thermal stress is compressive and relatively constant (0.215–0.275 GPa) over the temperature range investigated. The intrinsic stress is tensile and its origin is interpreted in terms of the grain boundary relaxation model. Calculations indicate a value of 0.84 GPa, using the grain boundary model, which is in fair agreement with the measured value. For the methane series, the tensile intrinsic stress decreases with increasing the methane fraction. The increasing compressive stress is ascribed to increased impurity (hydrogen and nondiamond phase carbon) incorporation with increasing methane fraction. 15N nuclear reaction analysis shows a linear correlation between hydrogen in the film and methane in the supply gas while spectroscopic ellipsometry shows a direct correlation between optically absorbing nondiamond (sp2) carbon incorporation and methane. For the temperature series, the intrinsic tensile stress increases with deposition temperature. The increase is ascribed to decreasing sp2 C incorporation with temperature, as confirmed by spectroscopic ellipsometry measurements.
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1800-1810 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A multichannel spectroscopic ellipsometer based on the rotating-compensator principle was developed and applied to measure the time evolution of spectra (1.5–4.0 eV) in the normalized Stokes vector of the light beam reflected from the surface of a growing film. With this instrument, a time resolution of 32 ms for full spectra is possible. Several advantages of the rotating-compensator multichannel ellipsometer design over the simpler rotating-polarizer design are demonstrated here. These include the ability to: (i) determine the sign of the p-s wave phase-shift difference Δ, (ii) obtain accurate Δ values for low ellipticity polarization states, and (iii) deduce spectra in the degree of polarization of the light beam reflected from the sample. We have demonstrated the use of the latter spectra to characterize instrument errors such as stray light inside the spectrograph attached to the multichannel detector. The degree of polarization of the reflected beam has also been applied to characterize the time evolution of light scattering during the nucleation of thin film diamond by plasma-enhanced chemical vapor deposition, as well as the time evolution of thickness nonuniformities over the probed area of the growing diamond film. In this article, a detailed description of calibration and data reduction for the new instrument is provided. Future applications of this instrument are expected for real time characterization of film growth and etching on patterned surfaces for microelectronics and on thick transparent substrates for large area displays and photovoltaics. © 1998 American Institute of Physics.
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 2029-2062 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In a typical reflection ellipsometry experiment, one characterizes the polarization state change that a polarized light beam undergoes upon reflection from a specular surface. This measurement provides ρ≡rp/rs, where rp and rs are the complex amplitude reflection coefficients of the surface for p- and s-polarized waves. Nearly 15 years have passed since the development of automatic ellipsometers along with the detailed calibration, error analysis, and data reduction procedures to be used with them. More specifically, these powerful instruments permit (1) determination of bulk dielectric functions and nondestructive depth profiling of static multilayered materials through measurements as a function of photon energy and (2) characterization of dynamic surfaces in adverse environments through measurements as a function of time at fixed photon energy. In the 15 intervening years, the major research thrusts in ellipsometry have been the exploitation of these instruments in materials and process characterization in diverse areas of materials science and electrochemistry. One of the simplest and most popular automatic ellipsometers is a photometric instrument in which one or more of the optical elements (polarizer, compensator, and/or analyzer) is designed to rotate continuously. In this article, the major developments in rotating element ellipsometry are reviewed since the first report of an automatic rotating analyzer instrument by Cahan and Spanier in 1969. The topics covered include rotating element configurations, calibration, characterization of errors and imperfections, absolute accuracy, data reduction, precision, and a review of the real-time applications accessible to these instruments. The sections on calibration, errors, and data reduction include new material and are written from a practical standpoint to assist in instrumentation setup and troubleshooting. The development and improvement of next-generation rotating element instruments that employ optical multichannel detectors to collect spectroscopic data on dynamic surfaces with time resolution as short as 5 ms now defines the forefront of research in this field.
    Type of Medium: Electronic Resource
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