5. Dislocations in Silicides

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.