(color online) (a) SEM of the top surface morphology and TEM of the cross-sectional structure of a polycrystalline Si–Ge thin-film grown by LPCVD at 650 °C; (b) High-resolution TEM of grains and grain boundaries. The inset picture shows the diffraction pattern of a grain; (c) X-ray diffraction (XRD) of Si–Ge thin-films. The vertical bars on the x axis indicate the corresponding patterns of Si and Ge single crystals; (d) The evolution of the grain size distribution of the Si–Ge thin-film with different annealing times, varying from 0.5 min to 60 min.^[53]