In this overview, our group's work on GaAs surfaces and interfaces is described. Cleaning processes for GaAs (001) surfaces in ultra-high vacuum, and Au/GaAs interface formation were studied by XPS, RHEED and RBS. PIXE, in combination with channeling, was used to determine the lattice locations of Zn and Si in GaAs and GaAlAs.
Developments of new lasers and improvements in laser performance have resulted in an expansion of laser applications, such as material processing, optical communication, nonimpact printing and therapeutic medical applications. In the material processing techniques for cutting, welding and heat treating of metals, infrared lasers such as CO2 and Nd : YAG lasers are now used as sources of thermal energy with high power density. Recently, very exciting developments have been taking place in the applications of lasers to micromaterials processing by photochemical treatment with UV excimer lasers. In this paper, the developments of new lasers and the laser beam processing of materials will be reviewed.
This paper reviews recent developments in microlithography, which is a key technology in manufacturing LSI and other electron devices. Newly developed exposure techniques such as electron beam, X-ray, and deep UV methods make it possible to delineate submicron features. To bring these methods into practical use, development of suitable resists is essential. Requirements for these resists such as sensitivity, resolution, and resistivity to dry etching are also discussed.
Imaging devices in the invisible light regions of ultraviolet, infrared and low light level are described and discussed, considering, in particular, the surface problems of photocondutive material. In the MIS blocking junction of a photoconductive target for an ultraviolet vidicon, a thin insulating film of MgF2 on a a-Se photoconductor and SiXNY on a-Si : H are shown to produce interfacial fields increasing sensitivity in short wave length region. In an infrared vidicon with a PbO-S target, it is shown that PbS, which forms a thin sucface layer on the textured Pb0 crystals, plays an important role and brings infrared sensitivity and resistivity sufficiently close to vidicon operation. For low light level use. SiO2-Si interface problems of a silicon intensifier target are described, and new type target with a hydrogenated amorphous silicon to crystalline silicon heterojunction is presented and discussed.
Recent researches and developement on particulate semiconductor photocatalytic reactions are reviewed. First, several important factors that have influence on photocalytic performance of semiconductor particles are pointed out. These factors are as follows, bandgap energy of photo-catalyst and photo-excitation, efficiency of h+-- separation and charge transfer to catalyst surface, band-edge locations of photocatalyst and redox potential of substrate, stability of catalyst and so on. Addition to these, fundamental studies concerning improvements of photocalytic property of semiconductor particles are described in terms of these factors. Next, application studies of photo-catalyst to organic synthesis and water treatment are introduced for amino acid synthesis, dehydro-dimerization reaction, secondary amine synthesis from primary amine, phenol derivative synthesis, degradation of halo-carbon compound contaminants and removal of heavy metal ions in water.
A scanning electron microscopic image suffers various degradation processes. Asa result, a SEM image is blurred and disturbed by electronic noise and can have unsatisfactory contrast. It is difficult to reduce the effects of these degradations only by various improvements in the intrinsic instrument. Certain image enhancements using digital image processing are the most powerful methods for improvement of the results of an unknown degradation process. Ways to compensate eachdegradation by using the appropriate image processing, have been tried. As a result of the application of these digital processings, we achieved better quality of the SEM image these were taken under high-resolution conditions by using combinations of these methods.
Problems in the expression of the Thomson-Freundlich equation are discussed, and it is shown that solubility or the vapour pressure in equilibrium with the spherical particle must be expressed as follows, ln (X/X0)=(3Vεi/γRT)andln(P/P0)=(3Vεs/γRT)Where, X is the solubility in the solution expressed in mole fraction of the material, P vapour pressure, γ particle radius, V molar volume, εi interface free nergy between solution and the spherical particle, ε, surface free energy of theparticle. The suffix zero attached to X or P means the equilibrium value of the solubility or vapour pressure for the system, γ=∞. We can use molar surface or interface free energy instead of (3Vεs/γ) or (3Vεi/γ) for a crystalline particle having its own crystal habit. The value of the right hand side of the equation is 1.5 times larger than that from Thomson-Freundlich equation. Using these results, grain growth phenomena expected to occur in the suspension of spherical fine particles were studied theoretically.