Analyzing residual stress in bilayer chalcogenide Ge(2)Se(3)/SnTe films

Chalcogenide thin film stacks of polycrystalline SnTe and amorphous Ge(2)Se(3) are analyzed for residual stress using X-ray diffraction. The as-deposited film stacks are annealed at different temperatures and the thermal dependence of stress is investigated. Stress evaluations are performed by employing the sin(2)j technique using a 2D area detector system. As-deposited samples are found to be compressively stressed and exhibit increasingly tensile thermal stress with increasing annealing temperature. Onset of crystallization of the bottom Ge(2)Se(3) layer is indicated by a sharp drop in the stress level in the 270 (o)C-360 (o)C temperature range, due to volume shrinkage associated with the crystallization. Diffraction patterns of samples annealed at different temperatures indicate compositional changes that are attributed to inter-diffusion of ions between the two layers. The XRD profiles of samples annealed at 360 (o)C and 450 (o)C indicate the formation of a Ge(2)Se(3)-SnTe solid solution. It is suggested that both, residual stress and temperature dependent compositional changes affect the measured d spacings.