Synchrotron X-ray diffraction observation of phase transformation during annealing of Si processed by high-pressure torsion

In situ observation of a phase transformation during annealing of Si containing diamond-cubic (dc) and metastable phases has been performed using synchrotron X-ray diffraction. Metastable body-centred-cubic (bc8) and rhombohedral (r8) phases were formed by high-pressure torsion. These metastable phases gradually disappeared when increasing the annealing temperature to similar to 180 degrees C while another metastable phase having a hexagonal diamond (hd) structure appeared at similar to 190 degrees C. High-resolution transmission microscopy analysis revealed that hd and dc grains were present after annealing at 200 degrees C. The results indicate that a phase transformation, mainly from bc8 to hd, occurred during annealing.

Automated summary

In situ observation using synchrotron X-ray diffraction was conducted to study the phase transformation in Si containing diamond-cubic and metastable phases during annealing. Metastable body-centred-cubic and hexagonal diamond phases were identified at different annealing temperatures, suggesting a phase transformation mainly from bc8 to hd during the process.