Twinning defects in spherical GeSi alloy nanocrystals

GeSi alloy nanocrystals embedded in amorphous SiO2 matrix were fabricated via magnetron sputtering method and subsequent high-temperature annealing. The crystallite morphology and microstructural defects of the alloy nanocrystals were characterized by high-resolution transmission electron microscope observations. It is observed that GeSi nanocrystals with an average diameter of ∼10 nm are mostly spherical and have low defect density. Such nanocrystals with twinning configurations, including single-twinning, multi-layer twinning, and five-fold twinning, were observed in ∼9% of total nanocrystals. The fabrication of spherical GeSi nanocrystals with low defect density is important for further studies in photoluminescence and acoustic phonon properties of the GeSi alloy nanocrystals.