材料期刊网

In a previous paper, we reported an investigation of the microstructure ahead of the crack tip induced during indentation at room temperature or GaAs single crystal and found that the crack tip is not atomically sharp. Dislocations may be activated around the crack tip under stress and these lead to a transformation from a crystalline lattice to a disordered structure, forming an amorphous hand between crack walls. It is proposed that the crack propagation is a result of decohesion by the amorphous hand, rather than sequential rupture of cohesive bonds. Here we present an HREM investigation of the atomic structure at the crack tip, including fast Fourier transformations (FFTs) and inverse fast Fourier transformations (IFFTs) performed on selected areas near the crack tip. The observations and analysis further confirm that the crack tip is not atomically sharp, and that the deformation is anisotropic along different crystalline planes.