Dislocations in Silicides

Abstract

Dislocations in epitaxial thin films and single crystals are considered in details in the CoSi2, NiSi2, MoSi2, WSi2 and TiSi2 silicides. Epitaxial single crystals can be obtained in ultra high vacuum by reacting a metal for example Co with a substrate Si (111) or NiSi2 formation on low index planes. Often—depending on conditions—dislocations dissociate into partials forming a stacking fault with the partial dislocations as indicated for MoSi2, WSi2 and TiSi2. A concept for dissociation (for example in MoSi2) is that dislocations move into a nonplanar configuration by a combination of glide and climb. The dislocation structure is orientation and temperature dependent and at high temperatures their structure might be irregular. Also, at the higher temperatures dislocation-vacancy interaction may occur resulting in restrictions in the dislocation line. Serrated flow stress is believed to be the result of dislocation-vacancy reaction. At the temperature where the stress-strain curves showed serrations, the dislocations observed are wavy, whereas in many of the structures (MoSi2, WSi2) the dislocations are straight.