The thermal stability of strained Ge films on Si substrate is critical for applications in electronic and optoelectronic devices.In this paper,the Ge thin films under tensile strain were grown on Si substrate with low temperature Ge buffer layer by ultra-high vacuum chemical vapor deposition.The TEM image indicates that there are low threading dislocations in the top high temperature Ge layers.The root-mean-square surface roughness of the Ge epilayer is about 1.2 nm which was evaluated by atomic force micro...