Analyzing Residual Stress in Bilayer Chalcogenide Ge₂Se₃/SnTe Films

Archana Devasia, Rochester Institute of Technology
Feiming Bai, Rochester Institute of Technology
Morgan Davis, Boise State University
Kristy A. Campbell, Boise State University
Surendra Gupta, Rochester Institute of Technology
Santosh Kurinec, Rochester Institute of Technology

Abstract

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 sin² ψ 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 °C–360 °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 °C and 450 °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.