Transmission electron microscopy analysis of planar faults on (001) planes in MoSi2 single crystals

Planar faults on (001) planes were formed during in-situ annealing and straining experiments on MoSi2 single crystals in a high-voltage electron microscope. As-received and pre-deformed crystals grown by either the float-zone or the Czochralski technique were exposed to temperatures between 400 and 1200degreesC. The faults are only formed if dislocations with 1/2<111> Burgers vectors are present. The faults and the bordering partial dislocations were characterized by a transmission electron microscopy contrast analysis. The two partial dislocations bordering a fault have different types of Burgers vector. It is suggested that the faults result from a dissociation reaction according to 1/2[111] = 1/2[110] + 1/2[001], leading to intrinsic stacking faults on (001) planes. Probably, similar microstructural mechanisms control both the formation of the faults and the flow stress anomaly of the <111>{110} slip system in MoSi2.