High-quality and thick Ge epitaxial films are grown on Si substrates utilizing the low-temperature(LT) buffer technique by ultrahigh vacuum chemical vapor deposition(UHV-CVD) and are characterized by atomic force microscope,X-ray diffraction,and Raman spectroscopy.The results show that the LT Ge buffer is rough due to the three-dimensional islands formations,but the misfit stress is nearly fully relaxed.Fortunately,the rough LT Ge surface is effectively smoothed by subsequent growth at elevated ...