Recent studies of Josephson tunnel junctions and related fabrication techniques are reviewed. Junction development is shifting from soft superconductors of lead alloys to hard and high Tc materials such as Nb and its compounds. Tunnel barriers, as thin as several tens of angstroms, are made of the native oxide of the electrode material, of oxidized a-Si, or of a foreign metal oxide. Superconducting electrons of the electrode located in a layer within a coherence length of the interface barrier contribute to tunneling. A well-defined interface is needed to control tunneling characteristics. Control is more difficult with high Tc superconductors having short coherence lengths (≤50Å) than it is with soft superconducting materials. Avoidance of interactions with the barrier material during the fabrication process is crucial for high quality junctions.
The electronic structures of ScH2, NiH2, YH2, and PdH2 with the cubic fluorite structure have been calculated using the discrete variational (DV) -Xα method. Clusters studied were [Me6H8] 4+ and [Me4H8] (Me : metallic atom). The level profiles of the [Me4H8] clusters revealed that Me-H bonding levels are located more than 4 to 7.5eV below the EF level. The results are generally in good agreement with UPS spectra previously observed for the Me-H system. The charge states were determined to be 1.2±0.4 for Me atoms and -0.6±0.2 for H atoms. The charge on the H atoms decreases as the mass of the Me atom increases in a particular group of the Periodic System. This is consistent with prediction from Pauling's electronegativity. The calculated level profiles and charge states are used to predict XPS spectra of the valence-band region. Analyses of spectral patterns showed that a photopeak of the Me-H bonding levels disappears as the number of d electron is increased.
The raw materials of the present composite films were silicone resins, Al2O3, TiO2, and talc. Upon heating, the hydrocarbon groups in side chains of silicone resins are gradually decomposed to form a solid residue involving siloxane bonds and decomposed hydrocarbon groups. Metal oxides in the solid residue appear on the surface. The present composite films heat-treated at 500°C show electronic conduction in dry air and act similarly to electrolytes in the presence of water vapor. Polymethylphenylsiloxane and polydimethylsiloxane were used as the silicone resins. The former is less decomposable than the latter at the same temperature. Therefore, the present composite films using polymethylphenylsiloxane heat-treated at 500°C had smaller specific surface areas and higher water repellency.
Fundamental aspects of Auger electron spectroscopy are reviewed. This review covers : the history of Auger electron spectroscopy, the electron impact ionization cross section of an atom, the relation between Auger electron yield and x-ray fluorescence yield, the inelastic mean free path of an electron in a solid, the energy of an Auger electron, the fine structure of the Auger spectrum, the chemical state effect and the effect of density of states of the valence band on the Auger spectrum, quantitative analysis using Auger spectroscopy, and the differential spectroscopic method.
Contact lensees are usually divided into two types. One is the hydrophobic hard contact lens made mainly from polymethylmethacrylate (PMMA), and the other is the hydrophilic soft contact lens made from polyhydroxyethylmethacrylate (PHEMA) or polyvinylpyrrolidone (PVP). Recently oxygen permeable hard contact lenses made from silicone have been widly used. Relationships between surface science and contact lenses are as follows; 1. deposits or coatings on the contact lens surface 2. wettability of the contact lens surface 3. surface hardness of the contact lens 4. tear evaporation from the contact lens surface 5. oxygen permeability For soft contact lenses, it is particularly important to solve the problems described in 1, 4, and 5 above. For hard contact lenses, the problems described in 2 and 5 are important and likewise for oxygen permeable hard contact lenses, the numbers 1, 2, 3, and 5 are important. If it is possible to solve some of these problems by the development of the surface science of the contact lenses, the contact lenses will be more comfortably availble to the patinents.