Thin films of 3 d transition metal oxides, namely, TiOx, MnOx, CrOx, CoOx and NiOx were prepared by electron-beam evaporation. All of them exhibited electrochromic behavior not only in the aqueous electrolyte but also in the non-aqueous electrolyte such as 1 M-LiClO4/γ-butylolactone. These films were characterized by electrochemical and spectrophotometric measurements. The electrochromic charge capacity was also determined. Among these 3 d oxides, NiOx films were found to provide excellent characteristics such as the highest coloration efficiency and the stability after 105 times color-bleach cycle.
Electron traps introduced into the surface region of n-type silicon by Schottky diode fabrication have been investigated with regard to the spatial distribution of the traps and the effect of annealing and etching. Concentrations of the electron traps exponentially decrease into those of the bulk of Au/n-Si Schottky barrier diodes. The trap distribution broadens during a series of isochronal annealing. The broadening of trap concentraion profiles can be interpreted in terms of the diffusion of mobile point defects associated with the electron traps. The effect of etching on the trap profiles shows that the point defects are driven into the bulk during the etching process. It is suggested that the electron traps are associated with hydrogen introduced into the silicon surface during etching.
The quantitative surface chemical analysis of Au-Cu alloys with N (E) curve of AES was studied. As for the Auger peaks at above 100 eV, the P/B method was applied to calculate the intensities. It was found that the P/B method was insensitive to the parameters measurements, and the values obtained by this quantitative chemical analysis were in good agreement with those by the ordinarily used dN (E) /dE method. However, the Auger peaks of Cu (60 eV) and Au (69 eV) at below 100 eV overlap, so that the peak fitting method was used to determine the surface compositions of the samples. The values from N (E) curves were in good agreement to those from dN (E) /dE curves also in this case.
The MBE growth conditions for Be doped GaAs layers are evaluated from quantum efficiency of the negative electron affinity photocathodes made of these layers. The quantum efficiency of the GaAs layers grown by molecular beam epitaxy method at various growth conditions was measured in reflection mode operation. High quantum efficiencies were obtained with Be doping levels between 1018 and 1019 cm-3 at high As/Ga beam flux ratios and high substrate temperatures.
The enhancement of the growth rate of Al2O3 has been observed during plasma anodization accompanied by optical excitation with low-power visible argon-ion laser light. The increase of the current efficiency with the laser light is approximately 20% of that without. And this enhancement of the oxide growth rate is considered to arise from promoting the generation rate of atomic oxygens, which contribute to the anodization as oxidizing species, in the plasma sheath near the specimen and/or on the specimen surface irradiated by the laser light. Although most of atomic oxygens are regarded to be generated by the dissociation of molecular oxygens colliding with plasma electrons, the laser excitation might help the cumulative dissociation of molecular oxygens.
We have calculated adsorption energies of a xenon atom adsorbed on metal surfaces taking both an attractive charge-transfer energy and repulsive exchange energy into account, where the matrix elements are evaluated by the method of Pollard and Toya. The calculated values of adsorption energies and work function changes due to adsorption are in qualitative agreements with the experimental data. The relation between our present theory and the simple charge-transfer theory is discussed.
Conventional methods for charge reduction by using an auxiliary electron beam or by placing metal diaphrams on the sample surface in the SIMS analysis of insulators, are either inpractical for a wide variety of materials or not completely effective. To solve these problems, the authors have developed a new insulator analysis method, combined with EBIC (Electron Bombardment Induced Conductivity) and formation of an electrically conductive path to reduce the sample surface charge. In this technique, a metal film about 40nm in thickness is deposited on the sample surface outside the analyzing area. Then electrons at an energy of about 3000 eV are bombarded both on the analyzing area and on the metal film. The EBIC layer is thus generated on the sample surface. The electron bombardment causes an electrically conductive path between the sample and the metal film, and therefore, charge accumulation on the sample surface is prevented. It has been found that this technique can be used successfully for the surface analysis of a wide variety of insulating materials, including oxides, nitrides and organic thin films.
A study on a GaAs buffer layer on a GaP (100) substrate in the two-step molecular beam epitaxial growth is described. In this growth technique, the GaAs buffer layer grown at a low temperature plays an important role in accommodating the lattice mismatch. We examine the influences of the growth conditions on the structural properties of the layers by varying growth temperature, As/Ga flux ratio and annealing temperature. The surface of the grown GaAs layers were amorphous-like for the growth temperature less than 125°C and As/Ga flux ratio over 3, and were crystalline for the temperatures higher than 150°C and the flux ratio of 3, or for 100°C and the flux ratio of 1. After being annealed at 500°C, the lattice mismatch of the former was accommodated perfectly, but the latter was not accommodated. AES analysis showed that an excess As was incorporated in the GaAs layer with the amorphous like surface, and the excess As was desorbed from the layer during the annealing for crystallization.
The ALE growth process of ZnTe is investigated with RHEED intensity observation. It is found that when the substrate temperature is sufficiently low, physisorbed Zn and Te adatoms are present on the Zn and Te-coverd surfaces, respectively. The ZnTe layers not less than monolayer grow during one cycle of ALE by the presence of these excess adatoms. Evaporation of the surface atoms occurs during growth suspension. First, the excess adatoms desorb, and then Zn and Te atomic layers sublime with different sublimation time constants. At high temperatures, the layer-by-layer evaporation occurs, as is verified by RHEED intensity oscillation during the sublimation process.
An investigation of surface electromigration of Cu overlayer on Si (111) was done by using scanning Auger electron spectroscopy. A Cu patch with a thickness of several monolayers was evaporated at room temperature on a cleaned Si (111) -7 × 7 substrate. The initial application of dc current through the substrate gave rise to an ordered Cu layer with approximately 2 monolayers, on the top of which three dimensional islands were grown. Then, directional spread of the ordered Cu layer toward the cathode occurred. This mass-transport, however, was suddenly terminated and, coincidently, the Cu Auger signal began to reduce in intensity. The tiansport process was discussed in terms of the Stranski-Krastanov growth and the intermixed interface.
Polyaniline was synthesized electrochemically from an aqueous solution of aniline containing perchloric acid. The obtained polymer films were treated with an aqueous solution of hydrazine or sodium hydroxide. Otherwise, anodic or cathodic potential were applied to the polyaniline films in an aqueous solution of perchloric acid. X-ray photoelectron spectroscopy (XPS) was utilized to investigate the differences in these various kinds of polyaniline films. A peak which changed its intensity according to the conductivity of the films and the amount of perchlorate ion contained was found at a higher binding energy position than that of the nitrogen photoelectron peak. The scheme of conductive polyaniline proposed by Bredas et al. give a reasonale explanation to these results.
The inner pore structure of etched aluminum foil electrodes of aluminum electrolytic capacitors has been successfully visualized by a new resin-replica method using an Araldite epoxy resin as the packing material. The most interesting point of this resin-replica method is that both the packing material and porous samples can be evacuated so that the resin monomer can effectively fill the pores. This made it possible to reveal the fine structure of porous aluminum electrodes. Since this epoxy resin is stable to HCl, H2SO4, and HF, this resin-replica method is adoptable to visualize the pore structures of various substrates such as porous electrodes, catalysts, and adsorbents.