Jun Aihara

Irradiation effects on yttria-stabilized zirconia irradiated with neon ions

Abstract In situ TEM observation was performed on yttria-stabilized zirconia during 30 keV Ne + ion irradiation at room temperature, 923 and 1473 K, respectively, and annealing was performed after irradiation. The observed results revealed clear difference in morphology of damage evolution depending on irradiation temperature. In the irradiation at room temperature defect clusters and bubbles were formed homogeneously at random, and defect clusters were formed earlier than bubbles. In the irradiation at 923 K bubbles and dislocation loops are formed heterogeneously almost at the same time. Moreover, bubbles existed almost only on the loop planes but were almost invisible outside of loop planes in the early stage of irradiation. In the irradiation at 1473 K only bubbles were formed and they grew remarkably with the increasing ion fluence. In annealing remarkable growth of bubbles were observed when temperature was raised from 1373 to 1473 K.

In-situ observation of surface blistering in silicon by deuterium and helium ion irradiation

Abstract Blistering processes on crystalline silicon surfaces were observed in situ by grazing incidence electron microscopy (GIEM) under deuterium (D + ) and helium (He + ) ion irradiation. In D + irradiation, the size and density of the blisters were significantly reduced in the continuously electron-illuminated area. This is attributed to the incident high-energy electrons, which suppress the formation of deuterium terminated cracks by electronic excitation effect. It was also found that irradiation at a higher ion flux give rise to catastrophic flaking before well-separated blisters were formed. In addition, the present study strongly suggests that the crack formation and propagation under D-irradiation start preferentially around the most heavily damaged depth rather than the peak projected range of the implanted D atoms.

Amorphization with ion irradiation and recrystallization by annealing of SiC crystals

Abstract The effects of reactive atoms on microstructural changes in polycrystalline sintered α-SiC thin film specimens irradiated with 30 keV N2+ or 20 keV Ne+ at RT (room temperature) and isochronically annealed (400–900∘C) after irradiation were studied by TEM. Irradiation-induced amorphization occurred during irradiation at RT with both N2+ and Ne+ irradiation. Bubbles were also observed to form, but nitrogen bubbles were more difficult to form than Ne bubbles. To investigate the effects of nitrogen on recrystallization behavior, the specimens irradiated with high dose and low dose of N2+ were annealed, respectively. High nitrogen content depressed the epitaxial growth from the crystalline region to amorphous region, while the dependence of the recrystallization behavior on Ne dose was not clearly observed.

Bubble formation with electron irradiation in SiC implanted with hydrogen or deuterium

Abstract The bubbles were formed and grew when SiC implanted with high fluence of hydrogen ion was irradiated with electron. In this study we tried to inspect the supposition that the energy deposition of the electron beam to hydrogen caused the migration of hydrogen and gave rise to bubble formation and growth. We used hydrogen (H) or deuterium (D) as implanted ion to change the cross section of the reaction that D or H is given energy by electron beam. The energy deposition cross section in the case of H is 2–3 times as large as that in the case of D. Bubbles were less likely to be formed and grow in the case of D than in the case of H. This result can be explained in terms of the difference of the concentration of the mobile gas atom caused by the difference of the energy deposition cross section, and does not contradict the supposition.

A Study of the Influence of the Specimen Anisotropy on the Thermal Diffusivity by the Laser Flash Method.

An analytical study on thermal diffusivity for anisotropic materials using a laser flash method was carried out to clarify the applicability of the method which has been established for an isotropic materials. A measurement error for anisotropic materials caused by the laser pulse intensity distribution was estimated analytically using a finite element calculation code. In this paper the analytical result on the measurement error of the anisotropic materials was presented and the applicability of the laser flash method to the anisotropic material was discussed.