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

Investigations of the plasticity,damage and fracture induced by micro-indentation 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 crack-tip deformation is anisotropic.