Indentation-induced Plasticity, Damage and Fracture in Si and GaAs Single Crystals

Investigations of the plasticity, damage and fracture induced by microa2indentation are reviewed. The principal findings are: (a) Micro-indentation may induce a transition from crystalline to nano-crystalline and amorphous structure, and there is a critical stress for this kind of transition. The shear stress, rather than the hydrostatic stress is proposed to be attributed to this transition. (b) There is a critical current density for the crystalline nucleation, and it is no related to the irradiation-induced temperature rise. (c) The crack-tip produced dislocations by during indentation is not atomically sharp, leading to crystal lattice distortion, and even to a transition from a crystalline lattice to disordered structure. An amorphous band with a width of 1-2nm between crack-walls is formed, and the crack propagation is then along the amorphous band, rather than sequential rupture of the cohesive bonds. (d) Fast Fourier Transformation (FFT)-SAED and corresponding Inverse-Fast Fourier Transformation (IFFT) fringe images from different lattice planes in selected areas of the crack-tip show that deformation around the cracka2tip deformation is anisotropic.