Alberto M. Guzman

Electrochromism in some thin‐film transition‐metal oxides characterized by x‐ray electron spectroscopy

Qualitative results of an x‐ray photoelectron and optical investigation of three thin‐film transition‐metal oxides, namely, WO3, MoO3, and V2O5 are reported. Data were obtained on films that were not colored and colored by an electrochromic process. The particular electrochromic coloration process used is electrolytic in nature and employs a sandwich‐structure electrochromic cell and electrolyte pool. The optical spectra show increased absorption in the visible (red) and near‐infrared spectral regions upon coloration. The photoelectron spectra for colored films exhibit a small band near the Fermi level and asymmetric band shapes for metal core‐level bands which are absent in films that are not colored. The new band and the asymmetric band shapes are attributed to the presence of a reduced‐state species caused by the presence of trapped electrons and metal bronze formation. Results from coloration with different electrolyte pools, i.e., H+, Li+, Na+, K+, Cs+, and Mg2+ electrolytes, are reported.

Trapped electrons in substoichiometric MoO3 observed by X-ray electron spectroscopy

Abstract Substoichiometric amorphous thin films of MoO3 in both the transparent and absorptive forms have been studied by X-ray electron spectroscopy. The transparent films can be colored blue (absorptive) electrically or by UV irradiation. The electron distribution curve of the blue film exhibits a small band near the Fermi edge which is absent in the transparent sample. This new band is attributed to electrons trapped in positively charged anion vacancies in the substoichiometric MoO3 lattice. This model provides an interpretation of the electrical conductivity and color of the films.

Field-enhanced emission and capture in polysilicon pn junctions

Abstract Large electric fields present in polysilicon pn junctions result in field enhancement of the emission and capture rates of traps in the depletion region. We used numerical integration to evaluate the enhanced emission rate and found that the field dependence of the emission rate could be approximated by a simple analytic expression. Calculation of the junction currents in forward and reverse bias were in qualitative agreement with measurements. However, the predicted magnitudes of the currents were considerably lower than those measured at low temperatures. This may be a consequence of interaction between traps, which results in a higher emission rate than predicted by the simple theory.

Influence of hydrogen implantation on the resistivity of polycrystalline silicon

The grain boundary passivation effect in polycrystalline silicon (polysilicon) thin films by hydrogen implantation has been studied. Boron‐doped polysilicon was implanted with low‐energy ions followed by low‐temperature annealing. Resistivity measurements show that the change in resistivity after implantation depends on the boron concentration in polysilicon. At low boron concentration ( 1×1019 cm−3), the resistivity increased after hydrogen implantation. This increase is ascribed to implant‐induced damage which cannot be totally recovered by low‐temperature annealing.

Investigations of implantation-induced changes in surface layers of epitaxial garnet thin films

Abstract Using newly improved FMR characterization techniques, we have established that mechanisms other than the implantation- induced stress are responsible for uniaxial anisotropy field change. We have measured λ 111 / M s and the crystalline anisotropy field H 1 in the implanted layer. H 1 is shown to decrease after implantation.

Characterization of aluminum/LPCVD polysilicon Schottky barrier diodes

Abstract The I-V characteristics of aluminum Schottky diodes made on LPCVD deposited polysilicon with a wide range of doping concentration (8.5 × 1015−1.7 × 1020 cm−3) have been investigated. Diodes with ideality factor n = 1.12 at room temperature were obtained with doping concentration ≤ 8.5 × 1016 cm−3. In contrast to large grain polysilicon, uniform I-V characteristics can be obtained across the wafer on fine grain LPCVD polysilicon. A barrier height of qφB0.73 eV at 300 K was consistently determined from both the I-V measurements and the specific contact resistance measurements. The contact resistance of aluminum/polysilicon contacts is well described by present theory except in the intermediate doping range.

The effect of ion implantation on epitaxial magnetic garnet thin films

Abstract Recently investigators have reported that ion implantation of magnetic garnet films causes magnetostrictive effects related to stress as well as effects not directly related to stress, such as the suppression of growth-induced anisotropy [1]. This suppression occurs especially in the case of heavy dose implantations, such as 2×10 14 at/cm 2 Ne for example. We report here on the measurement of the stress contribution to implantation-induced anisotropy field change and the total anisotropy field change in films which have compositions suitable for 1 μm and 0.5 μm diameter bubbles. We also report on the measurement of the crystalline anisotropy field in the implanted layer. Films were implanted with deuterium and oxygen ions. Motivation for this choice is discussed.

THE CARNEGIE MELLON TRUCK SIMULATOR: A TOOL TO IMPROVE DRIVING SAFETY

Carnegie Mellon Driving Research Center, together with ISIM, is presently involved in the design and development of an Advanced Human Factors Research and Driving Training Research Facility. This facility has been designed to address human factors issues and driver training issues. Human factors interests include developing countermeasures for fatigue and driver/vehicle interface issues. Driver training issues include validating the usefulness of simulators for driver training, developing effective curricula and investigating simulator fidelity needed for effective training. A key component of the facility is the Carnegie Mellon TruckSim that will be capable of simulating a variety of commercial and emergency vehicles using interchangeable cabs mounted to a common motion platform. TruckSims modular configuration will allow for rapid and cost effective design of experiments and training scenarios. A first research programme to evaluate fatigue countermeasures is presented as an example. (A) For the covering abstract of the conference see ITRD E203705.