Microsc. Microanal. Microstruct. 4, 331-339 (1993)
DOI: 10.1051/mmm:0199300402-3033100

Structural change induced near surfaces of α-Al2O3 during electron irradiation

Y. Tomokiyo¹, T. Manabe¹ et C. Kinoshita<sup>1, 2

1</sup>  Research Laboratory of High Voltage Electron Microscope
²  Department of Nuclear Engineering, Faculty of Engineering, Kyushu University, Fukuoka 812, Japan

Abstract
A structural change produced by electron irradiation near surfaces of α-Al 2O3 was observed through high resolution electron microscopy and electron diffraction. Initially smooth surfaces become rough during TEM observations at 200 and 400 kV and holes appear with a prefered orientation of growth. Planar defects are also produced near the surfaces; they appear as dark- or bright-lines parallel to the (001) plane when the specimen is observed along the [110] direction, and they are also visible along the [001] direction as a periodic modulation of bright dots. The defects give rise to streaks and extra spots in electron diffraction patterns along [110] and [001], respectively. A formation mechanism and model of the defects were proposed; the defects are induced by inelastic scattering on Al plane parallel to (001) through rearrangement of Al ions and Al-vacancies. Three quaters of the atomic sites of the Al plane are occupied by Al ions and one quater is vacant, while 2/3 of the sites are filled with Al ions in perfect α-Al2O3.

PACS
6180F - Electron and positron radiation effects.
6837L - Transmission electron microscopy (TEM) (including STEM, HRTEM, etc.).
0778 - Electron, positron, and ion microscopes; electron diffractometers.
566114 - Electron diffraction and scattering.

Key words
Electron beam effects -- Electron irradiation -- TEM -- High-resolution methods -- Electron diffraction -- Radiation damage -- Defect formation -- Planar defects -- Crystal structure -- Alumina -- Al2O3 -- Al O


© EDP Sciences 1993