Crack tip dislocations in silicon characterized by high-voltage electron microscopy

The nature of crack tip dislocations and their multiplication processes in silicon crystals have been examined by using high-voltage electron microscopy. Cracks were introduced by the Vickers indentation method at room temperature, and the specimen indented was annealed at high temperatures to induce dislocation generation around the crack tip under the presence of residual stress due to the indentation. In the specimens annealed, fine slip bands with the step heights of around 1 nm were formed along the (111) slip planes near the crack tip. The crack tip dislocations observed were characterized by matching their images to those simulated, and it was found that two different slip systems were activated even in the early stage of dislocation emission. With the increase in the number of crack tip dislocations, more complicated dislocation configurations such as dislocation tangles were formed around the crack tip, showing the beginning of multiplication of crack tip dislocations which causes effective crack tip shielding.