Residual stress, strain and defects: its effect on the band gap of poly-Ge thin film realized on glass via Au induced layer exchange crystallization process

Residual stress in polycrystalline-Ge thin film realized on glass substrate using Au-induced layer exchange crystallization process is evaluated using x-ray diffraction based technique. The measured stress is found to be tensile in nature, from which we delineate and discuss the extrinsic thermal and intrinsic growth stresses. An in-plane biaxial tensile strain similar to 0.15% was estimated to be endured by the polycrystalline-Ge thin film. The narrowing effect that such strain and the crystallization or growth-related defects have on the optical energy band gap of the polycrystalline-Ge thin film is elucidated.