Twinning Ge0.54Si0.46 nanocrystal growth mechanism in amorphous SiO2 films

Ge 0.54 Si 0.46 alloy nanocrystals (NCs) with different twinning structures are synthesized by magnetron sputtering followed by high temperature (>1100 °C) annealing and rapid cooling. The local strain induced by rapid cooling enables neighboring NCs to coalesce quickly. Because of insufficient time to form individual structures, a leading twinning interface forms inevitably in the interior of the NCs. The twinning NCs with large surface free energies reconstruct for energy optimization at high temperature. Consequently, the twinning layer thickness shrinks slowly, finally transforming into untwined stable NCs with the lowest surface free energy. Our experimental observations are corroborated by theoretical calculation.