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We have developed a parallel-plate rheometer in a magnetic-disk drive configuration constructed of optically transparent materials and operating with a very small gap for measurements at very high shear rates. The friction force at the disk–slider interface has been measured as a function of sliding speed while the film thickness was monitored in situ using a capacitance technique. The shear rate is calculated from the film thickness and the sliding speed. A thin film can be applied on the disk, which allows very high-shear-rate measurements at low sliding speeds with negligible viscous heating. Both disk and slider have been made of optically transparent material to allow optical measurements simultaneously with the rheological measurements. In the present mode, the apparatus is set up for simultaneous rheometery and birefringence measurements on a thin film of polymer lubricant. Rheology and birefringence measurements were made on a perfluoropolyether lubricant over a range of strain rate from 103 s−1 t...

A quantitative relationship has been experimentally determined correlation the resolution degradation of p‐type coaxial high‐purity germanium detectors to the concentration of residual hole‐trapping point defects. Detector diameters ranged from 48 to 65 mm, and the average electric‐field strength was 1500 V/cm. The concept of a ‘‘standard level’’ is proposed, which originates in the similar capture kinetics of many commonly observed residual acceptors in high‐purity germanium. A method for calculating the electric‐field dependence of hole capture is presented and used to compare the data reported here with published modeling results parameterized by the mean‐free‐drift length. Good general agreement is found.

A series of SiO2 films with thicknesses varying from 3 to 325 nm have been grown on silicon using standard dry oxygen growth techniques and examined using the two‐channel polarization modulation ellipsometer, which has increased sensitivity for very thin insulating films on silicon. Using a biased estimator fitting technique, the ellipsometric data are fit to either an air‐SiO2‐Si model or an air‐SiO2‐interface‐Si model, where the optical functions of the SiO2 layer are approximated using an isotropic one‐term Sellmeier approximation. The results from the one‐term Sellmeier approximation show that the refractive index of the SiO2 layer increases with decreasing film thickness, while the interfacial layer thickness decreases with decreasing film thickness.

Thin films of ZnS grown on GaAs by laser ablation are examined using spectroscopic two‐channel polarization modulation ellipsometry (2‐C PME). It is found that variations in the film thickness over the illumination spot result in the quasidepolarization of the incident light, which can be measured directly using 2‐C PME. Quantitative fits of the ellipsometry data using a distribution‐of‐thicknesses model agree with independent reflectivity measurements of the thickness gradient, and allow for the accurate determination of the optical functions of the ZnS film.

A comparative study of arF- and KrF-laser deposition of amorphous diamond-like carbon (DLC) films and relevant carbon plasmas has been performed. Spectroscopic ellipsometry and EELS analysis of the DLC films deposited on Si and NaCl substrates were utilized to characterize the high quality arF- and KrF-laser deposited films (up to 84% of sp3 bonded carbon in 7 J/cm2 -ArF-laser DLC film). Gated ICCD imaging, luminescence and ion current probe diagnostics of the carbon plume have revealed quite different properties of carbon plasmas generated by arF- and KrF- lasers. KrF-laser (6.7 J/cm2) irradiation produces a less energetic carbon plasma containing larger amounts of C2 and probably larger clusters compared with arF-laser irradiation at the same energy fluence. We conclude that the more energetic and highly-atomized arF-laser carbon plasma results in the better diamond-like properties.

A procedure has been developed to determine the optical functions of thin films from spectroscopic ellipsometry data.

Generally, spectroscopic ellipsometry data are compared with a model of the sample surface by using a nonlinear least-squares fitting procedure to determine characteristics of the surface, which include thin-film thickness and fractions of individual constituents in the layers. Usually, an unbiased estimator (i.e., without any spectroscopic weighting) is minimized to determine the parameters of the fit. In this paper, the use of the biased estimator in the fitting of spectroscopic ellipsometry data is examined and is applied to data from two-channel polarization modulation ellipsometry experiments. By including the error in the estimator, the more accurate regions of the spectrum are weighted more, and the ellipsometric data can be expressed in the most appropriate way (i.e., as complex P, W and A, complex e) without affecting the results of the fit. In addition, a goodness-of-fit can be calculated, which indicates whether a more complicated model is necessary or whether competing models are statistically different. Several thin films of SiC>2 on Si will be discussed as examples.

Two-channel spectroscopic polarization-modulation ellipsometry measurements have been made on four different glasses (a fused SiO2 glass, a fine-annealed BK-7 glass, an indium-lead-phosphate glass, and a germanium-arsenic-selenium glass). It is shown that this technique is sensitive to thin surface layers and that these surface layers can be modeled by using the Bruggeman effective-medium theory with 50% glass and 50% voids. If we correct the experimental spectra for this surface layer, the refractive index of the sample can be determined to ±0.002 in the transparent region. For wavelength regions where the material is normally opaque, the ellipsometric data can be corrected for this overlayer, thereby increasing the accuracy of the determination of both the refractive index and the extinction coefficient.

A technique has been developed for continuously carrying out time‐resolved ellipsometric measurements on the nanosecond timescale. Using this technique, the optical properties of silicon have been measured during and immediately after pulsed excimer (KrF, λ=248 nm) laser irradiation. From these data the optical functions of liquid silicon at λ=632.8 nm have been determined to be n=3.8 and k=5.2±0.1, in minor disagreement with the results of Shvarev, Baum, and Gel’d [High Temp. 15, 548 (1977)]. The surface temperature before and after melting was also continuously determined by comparing these results with elevated constant‐temperature measurements of the optical functions. The results demonstrate that time‐resolved ellipsometry is a powerful technique for examining changes in optical properties on the nanosecond timescale.

Calculations are presented for the effect of various antireflection coatings on silicon solar cells. In particular, the relationship of different quantum efficiencies and illumination spectra to the optimum film thickness(es) and to the maximum collectible current is examined. It is found that the ratio of the collectible current to the maximum possible current (with the reflectivity = 0 over the entire solar spectrum) is larger if the solar cell has a poor spectral quantum efficiency and/or the illumination spectrum is peaked (such as from an ELH lamp). Single- and double-layer coatings are examined, and it is found that the double-layer coatings are less sensitive to errors in the coating thicknesses, as well as yielding more collectible current.

The effect of lithium on the electrical properties of polycrystalline silicon has been studied using scanning light spot and Hall‐effect measurements. It was found that the addition of lithium to polycrystalline silicon significantly improved the majority‐carrier mobility and reduced the minority‐carrier recombination at the grain boundaries. A possible mechanism for the interaction of Li with grain boundaries is discussed.

The optical properties of liquid silicon and germanium have been determined at several laser wavelengths from 1.96 to 3.71 eV, using time‐resolved ellipsometric measurements during pulsed laser melting. The results from these transient melting experiments are compared with results from the literature for materials held above their melting temperatures for long periods of time. The results for liquid germanium agree well with those of J. N. Hodgson [Philos. Mag. 6, 509 (1961)], but the results for liquid silicon disagree with the results of K. M. Shvarev, B. A. Baum, and P. V. Gel’d [High Temp. 15, 548 (1977)].

Single-crystal p+ -n-n+ silicon solar cells with AM1.5 efficiencies exceeding 19.5 percent have been fabricated using glow-discharge implantation and pulsed excimer laser annealing, together with techniques for reducing the recombination current. These techniques include extrinsic passivation by thermal oxide growth and fine-line photolithography for metallization in order to reduce the area of metal-silicon contact. These are the highest efficiency ion-implanted nonconcentrator cells reported to date and to our knowledge they are the highest efficiency p-on-n cells made by any technique.

The refractive index of silicon has been measured at elevated temperatures at several different laser wavelengths of the HeNe and the Ar+ cw lasers. This data, along with the reinterpretation of polarization modulation ellipsometry data, shows that the refractive index is linear with temperature (from 25 to ∼750 °C) and that the temperature coefficient of the refractive index increases as the wavelength of light decreases.

The optical absorption coefficient of silicon has been measured at the HeNe near‐infrared line (λ = 1.152 μm) from room temperature to 1140 K. The results are compared with the previous less extensive data in the literature, and with the formulation given by Macfarlane et al. [Phys. Rev. 111, 1245 (1958)]. It is found that the absorption is described very well by phonon‐assisted indirect transitions across an energy gap having the temperature dependence described by Thurmond.

Quadrupolar‐broadened NMR spectra were obtained for 0‐17, B‐10, and B‐11 in B2O3 glass using samples specially enriched in 0‐17 and B‐10. Lineshape analysis of the 0‐17 spectra indicates the presence of two oxygen sites. Site one has coupling constant Qcc=4.69 MHz and asymmetry parameter η=0.58, corresponding to oxygen atoms in boroxol rings; site two is characterized by Qcc=5.6 MHz and a large distribution in η about the value η=0.2, corresponding to oxygen atoms connecting boroxol rings. From one of the features of the B‐10 spectrum, the distribution of the boron coupling constants is obtained centered about the value Qcc=5.51 MHz (corresponding to Qcc =2.64 MHz for B‐11). A distribution about η=0.12 is postulated for the boron asymmetry parameter which fits the remainder of the spectrum. These distributions are shown to agree with the B‐11 spectrum.

A simple implementation of a commercially available high‐voltage power supply is described whereby the power supply can be used for voltage biasing of a photomultiplier tube operating either in a constant dynode voltage or in a constant output current mode. In the constant current mode, low frequency fluctuations in the current are suppressed without attenuation of a high frequency signal. Both the phototube output current and the dynode voltage can be set by external voltages in the range from −10 to +10 V, making computer control easy with standard digital‐to‐analog converters.

The equations governing ellipsometry measurements made with a photoelastic modulator are presented in a simple but general form. These equations are used to study the propagation of both systematic and random errors, and an assessment of the accuracy of the ellipsometer is made. A basis is provided for choosing among various ellipsometer configurations, measurement procedures, and methods of data analysis. Several new insights into the performance of this type of ellipsometer are supplied.

A comparative study is made of four methods for treating the graded nature of the Si–SiO2 interface in the analysis of ellipsometry data: (1) the stratified-media model, in which the total number of layers is large (>10); (2) the three-boundary approximation, in which the interface is treated as a single, homogeneous layer; (3) the two-boundary approximation, in which the effects of the interface are incorporated into an effective oxide-layer thickness; and (4) the integral-equation method, approximated to first order, of Plieth and Naegele [ Surf. Sci.64, 484 ( 1977)]. The Si–SiO2 transition layer is assumed to have optical functions that vary monotonically between those of Si and SiO2 in six different ways. In each of the six cases, the ellipsometry parameters ψ and Δ are computed for the air–SiO2-interface bulk-Si system by using the four methods stated above. The results illustrate the sensitivity of ellipsometry to the interface layer and reveal that the interface layer must be properly taken into account for accurate analysis. It is concluded that the three-boundary approximation is not necessarily more accurate than a judiciously applied two-boundary model and that the first-order approximation of Plieth and Naegele introduces sizable errors at short wavelengths for the Si–SiO2 interface.