Direct observation of the cleavage plane of sapphire by in-situ indentation TEM

Abstract

TEM in-situ indentation experiments were applied to directly observe the atomic structures on the cleavage planes of sapphire, and the structures were determined by HRTEM image simulation. It was found that cracks mainly propagate along the low index planes of sapphire, forming the atomic scale steps on the cleavage planes, and the atomic structures are dependent on the crystal orientation. In addition, the surface structures of the cleavage planes were found to be reconstructed in the vicinity of the respective surfaces. For the (1120) cleavage plane, the surface is composed of Al–O–Al cluster to form the complicated and metastable Al rich surface.