各種サファイアに対するkeV領域電子線照射効果

抄録

Various types of single-crystalline α-Al₂O₃ have been investigated on bleaching and cracking effects of keV electron beams using scanning electron microscope (SEM) and cathodoluminescence (CL) measurements. These electron-irradiation-induced effects observed at room temperature were different among four types of sapphires examined, namely, Be-diffusion-treated natural, untreated natural, synthetic orange, and synthetic red sapphires. The bleaching phenomenon occurred at electron dosages and the surface cracking phenomenon was subsequently observed at substantially higher dosages. The former was reversible so that an appropriate annealing in an oxygen atmosphere completely removed the bleached areas whereas the latter was a permanent change in structure that was not able to be recovered at all by such a treatment. It is found from these evidences that the crystalline quality of each specimen was well correlated with its beam-dose dependences of the electron-beam-induced phenomena observed. It should be noted that such electron-induced effects were almost completely reduced by the presence of a thin conductive layer on the insulating specimen surfaces.