Formation of metastable bc8 phase from crystalline Si0.5Ge0.5 by high-pressure torsion

Abstract Si0.5Ge0.5 crystals were subjected to severe plastic deformation using high-pressure torsion (HPT). A metastable body-centered-cubic phase having a bc8 structure was formed by HPT processing with anvil rotations. High-resolution transmission electron microscopy analysis revealed that nanograins having diamond-cubic (dc) and bc8 phases were present in the HPT-processed sample. The bc8 phase was reverse transformed back to the dc phase after annealing. The resistivity of the crystalline Si0.5Ge0.5 (~9 × 10−3 Ω·cm) increased by roughly a factor of 6 after compression, and remained on the same order of magnitude but decreased slightly after 10 anvil rotations despite the grain refinement. These results indicate that the electrical behavior of bc8-Si0.5Ge0.5 is similar to that of bc8-Si.