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We report experiments for recovery of the specular beam intensity in reflection high-energy electron diffraction (RHEED) after exposure to As flux over a pre-deposited Al film of thickness equivalent to several monolayers on a GaAs or AlAs substrate in a temperature range between room temperature and 700°C. Four types of recoveries have been found. They form a phase diagram with the substrate temperature and the Al film thickness as parameters. The phase diagram suggests that the thinner Al film on a substrate has lower melting temperature than the bulk melting point of Al if we assume that As atoms do not enhance diffusion of Al atoms in a solid Al film.

歯周病原菌といわれる7菌種 (Bacteroides gingivalis, Bacteroides intermedius, Bacteroides melaninogenicus, Fusobacterium nucleatum, Actinobacillus actinomycetemcomitans, Capnocytophaga ochraceae, Eikenella corrodens) 及び対照として2菌種 (Streptococcus intermedius, Pseudomonas aeruginosa) に対して, ポビドンヨード液 (10% PVP-1) を用いて, その殺菌効果をin vitroで検討した。希釈倍率は原液及び100倍, 400倍, 800倍, 1, 600倍, 3, 200倍, 6, 400倍, 12, 800倍までを設定し, PVP-I接触時間は15秒, 30秒, 60秒とした。その結果, 歯周病原菌7菌種, 対照2菌種に対するPVP-Iの殺菌効果は, 400倍希釈, 15秒 (最少接触時間) で殺菌効果が認められた。このことは, 口腔粘膜の殺菌及び歯周ポケット内へのPVP-I薬液投与の有効性を示唆するものである。

Anisotropy in surface migration of Ga atoms on GaAs (001) has been found by a study of the reflection high-energy electron diffraction (RHEED) intensity oscillations. The RHEED intensity oscillations have been investigated on GaAs (001) vicinal surface inclined to both directions of [110] and [1 1 0]. After the method given by Neave et al. [Appl. Phys. Letters 47 (1985) 100], it is found that the diffusion coefficient at [1 1 0] azimuth is 4 times larger than that of [110]. Isotropic surface diffusion of Ge on Ge (001) is also discussed in comparison with GaAs (001).

The intensity oscillation of reflection high-energy electron diffraction was observed during the growth of AlxGa1-xAs accompanying the incorporation of As into an Al and Ga mixed layer on a GaAs substrate. The degree of oscillation depends on the Al fraction of the mixed layer and on the substrate temperature. Incorporation of As into Al on an AlAs surface was also investigated to compare with the case of As incorporation into the mixed layer on the GaAs substrate. It was found that mixing of Ga in the Al metal layer strongly lowered the low-temperature limit of the intensity oscillation and also increased the oscillation magnitude. This will be attributed to a large migration of Ga atoms rather than Al atoms.

Plastic-clad fiber is a fiber of the step-index type that consists of an inner core of high purity synthetic quartz and an outer coating clad of plastic material which has a lower refractive index than the inner core.

Reflection high‐energy electron diffraction (RHEED) intensity oscillation during sublimation of GaAs is observed at high substrate temperatures above 690 °C. This post‐growth RHEED intensity oscillation suggests that the sublimation occurs layer by layer. One period of this oscillation precisely corresponds to sublimation of one monolayer. Aluminum arsenide acts as a sublimation stopper. The sublimation rate was measured accurately as a function of substrate temperature.

Reflection high‐energy electron diffraction (RHEED) intensity oscillations during Si molecular beam epitaxy (MBE) are observed for the first time. It is revealed that stable RHEED intensity oscillation exists during the MBE growth of a single‐element semiconductor. The stable oscillations were observed only after preheating treatments. The substrate temperatures for the oscillation were from as low as room temperature to 1000 °C. One period of the oscillation corresponds to atomic‐layer or biatomic‐layer growth on the concerned surface. Oscillation of more than 2200 periods (∼6000 A) was observed. One oscillation period can be as slow as 38 min.

Tunnelings of X-point electrons are observed in MBE grown AlAs-well, Al 0.5 Ga 0.5 As-barrier triple barrier diodes. In this structure, X-point minima are the lowest conduction band. At 85 K, tunneling peaks are observed both in the thicker and the thinner barrier diode. Although there is a large difference in current density, bias voltages for respective current peaks are very similar for these two diodes. This rules out the possibility of resonant tunnelings through a parasitic Γ -point quantum well in a Al 0.5 Ga 0.5 As barrier. Five current peaks are identified and these are assigned as the tunnelings from the ground subband in one well to the ground, the first excited, and the second excited subband in the other well. Comparison with a Γ -point resonant tunneling diode shows that the electron mass which defines the subband energy levels in the well is the X-point transverse mass.

1. One of the major origin of H 2 generation in jacketed fiber is confirmed to be the decomposition of residual Si-H groups in the silicone resin of the coated fiber, by the methods of Infra-red absorption analysis, Gas chromatograph analysis and the study of increase in loss spectra.

Long lasting RHEED oscillations during MBE growth of GaAs and Al x Ga1-x As are observed. Using these oscillations, accurate measurements of GaAs, Al x Ga1-x As growth rates and the Al mole fraction x were performed during the growths. The phase of the RHEED oscillations was analyzed by computer and molecular beam shutters were operated at a particular phase. This computer controlled phase-locked epitaxy (PLE) was applied to grow precisely defined (GaAs)2(AlAs)2 bi-layer superlattices. Raman scattering spectra showed split lines characteristic of superlattices. This PLE method is invulnerable to molecular beam fluctuations.

The effect of an undoped spacer layer up to 300 A thick adjoining a triple-barrier diode is studied. Larger peak-to-valley ratios and smaller full-widths at half maximum (FWHM), compared to conventional triple-barrier diodes, are obtained for the resonant current-peaks in these samples. It is explained that a main cause of the peak broadening is the random distribution of silicon ions in the heavily doped layer adjoining the barrier.