Investigation of the microstructure ahead of a crack tip induced during indentation at room temperature of a GaAs single crystal had shown that the crack tip was not atomically sharp. Dislocations could be activated around the crack tip under stress and these led to a transformation from a crystalline lattice to a disordered structure; forming an amorphous band between crack walls. It was proposed that the crack propagation was a result of decohesion by the amorphous band, rather than sequential rupture of cohesive bonds. Here, a high-resolution electron microscopic investigation of the atomic structure at the crack tip was presented, including fast Fourier transformations and inverse fast Fourier transformations performed on selected areas near the crack tip. The observations and analysis further confirmed that the crack tip was not atomically sharp, and that the deformation was anisotropic along different crystalline planes.

Atomic Structure and Deformation Behaviour around the Crack Tip Induced during Indentation of GaAs Single Crystal. Y.B.Xu, Z.C.Li, H.Zhang: Philosophical Magazine Letters, 2008, 88[1], 1-8