Shigeyuki Yamamoto

Novel Silicone Polymeric Material with High Thermal Stability for Optical Waveguides

The optical loss and refractive index controllability of a novel silicone ladder copolymer (polyvinylphenylsilsesquioxane: PVSQ) were studied with respect to the application of the copolymer to optoelectronic components. PVSQ copolymers were prepared from trichlorophenylsilane and trichloro (vinyl) silane in the various mol ratios. They had a ladder structure consisting of siloxane bonds as the main chain and phenyl groups or vinyl groups as the side chain. PVSQ demonstrated excellent transparency at the wavelengths used in optical communication, 0.6–1.7 µm. The optical losses of PVSQ with 5 mol% vinyl group content in the side chain, were 0.99 and 1.05 dB/cm at the wavelengths of 1.30 and 1.55 µm, respectively. The in-plane refractive index of the polymers at 0.65 µm could be controlled to between 1.558 and 1.466 by changing the contents of phenyl groups and vinyl groups in the side chain. The out-of-plane refractive index could also be controlled to between 1.562 and 1.466. The thermal decomposition temperature of PVSQ, defined as that at which 10% weight loss occurred in N2 atmosphere, decreased with increasing vinyl group content, but all still showed decomposition temperatures above 500°C, ensuring sufficient thermal stability for polymer waveguide applications. Furthermore, the correlation between the vinyl group content and the refractive indices of the PVSQ polymers were discussed based on results of the molecular orbital (MO) calculations. The MO calculations were found to be useful for qualitative estimation of the change in the refractive index of compounds with a systematic derivative structure, such as PVSQ polymers.

A Versatile Photostimulated Exoelectron Emission Microscope as Applied to Observing Mechanical Damage on Aluminum Surfaces

A photostimulated exoelectron emission microscope has been developed, which enables us to observe mechanically-damaged surfaces in two modes; in one mode it forms a direct image on a phosphor screen by means of an electron optics system including an image intensifier, and in the other it indicates the spatial distribution of the emission intensity or of an electron energy spectrum obtained by scanning the specimen surface with a light spot. Through observation of aluminum surfaces damaged either by tensile deformation or by friction, it has been demonstrated that the microscope can be operated as easily as a scanning electron microscope and the exoelectron image gives information as to how fresh and critical each damage is.

Versatile Photostimulated Exoelectron Microscope and Its Application

A versatile photostimulated exoelectron microscope has been developed which has enabled us to observe a photostimulated exoelectron image and the corresponding secondary electron image of the same region. Through observations of various metal surfaces mechanically damaged by scratching, rubbing, blasting, or tensile deformation, it has been demonstrated that the exoelectron image gives information regarding the damage freshness.

Measurement of Surface Fatigue Damage by Using Photostimulated Exoelectron Emission

Commercial aluminum (purity 99.5 %) specimens are fatigued in the vacuum of 1×10-5 Torr and the distribution of the photostimulated exoelectron emission (PSEE) on the specimen surface is measured by scanning the surface with a small light spot. In the range of cyclic stress and strain amplitudes examined in the present investigation, the PSEE increases up to approximately 10 % and 30–52 % of fatigue life in the load-controlled mode and the straincontrolled mode, respectively saturates or decreases slowly with additional cycling and finally increases drastically at the failure of the specimen. The relation between the PSEE and fatigue properties in vacuum is discussed.

Effect of Deuteron Irradiation on the Magnetic Anisotropy of Thin Ni-Fe Films

Thin films of Ni-Fe (Ni 50–100%) are irradiated by 250 kV-deuterons below 50°C. The anisotropy constant, Ku, of normal incidence films reaches a saturation value with 10–20 minutes irradiation (1016 deuterons/cm2), easy axis being parallel to the magnetic field applied during irradiation. The saturation value of Ku as a function of Ni concentration is explained well by the atom and vacancy orders. The change in Ku of oblique incidence films is independent of the field direction during irradiation. In the case of 30° incidence, Ku increases (Ni 90%) at the initial stage of irradiation, and after the initial change |Ku| decreases monotonously. In the case of 60° incidence, a similar result is obtained except that the initial stage change in Ku with irradiation is not so clear. These results are suspected to be due to a change in the columnar structure caused by the vacancy migration.

Cylindrical Mirror Analyzer for Measuring Energy Spectrum of Photostimulated Exoelectrons

A cylindrical mirror analyzer (CMA) for measuring the energy spectrum of photostimulated exoelectrons has been designed. The CMA is equipped with a mirror mounted at an angle of 45° to the electron optical axis within an inner cylinder. Through the mirror, ultraviolet light can be focused on the surface of a specimen. Typical results obtained with this CMA are presented.