Analyzing residual stress in bilayer chalcogenide Ge2Se3/SnTe films

Chalcogenide thin film stacks of polycrystalline SnTe and amorphous Ge2Se3 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) psi 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 Ge2Se3 layer is indicated by a sharp drop in the stress level in the 270 degrees C-360 degrees 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 degrees C and 450 degrees C indicate the formation of a Ge2Se3-SnTe solid solution. It is suggested that both, residual stress and temperature dependent compositional changes affect the measured d spacings. (C) 2009 Elsevier B.V. All rights reserved.