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The amorphized region of single-crystal silicon (c-Si) induced by Vickers indentation has been studied cross-sectionally by transmission electron microscopy (TEM) and high-resolution electron microscopy (HREM). A comparison between the V-shaped profile of the amorphous region and the stress isobars under the indenter shows that the deviatoric stress plays a significant role in the formation of amorphous silicon (a-Si). A number of defects near the crystalline/amorphous (cla) interface, and the refinement and rotation of grains at local regions, are observed by HREM. The distortion of lattice fringes in the c-Si region and the domains characterized by distorted lattice in the a-Si region near the interface as well as continuous transition from the crystalline to the amorphous region at the interface are also observed. A possible mechanism of defect-induced or heavy-deformation-induced amorphization of silicon under indentation is suggested. (C) 1999 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.