Evidence of Germanium precipitation in phase-change Ge1−xTex thin films by Raman scattering

Abstract

In situ annealing Raman scattering is used to evidence germanium postcrystallization in the crystalline phase of Ge-rich phase-change GeTe thin films. Both reflectivity and Raman scattering show that the crystallization temperature of the as-deposited amorphous phase increases with increasing Ge content going from Tc=180 °C (Ge0.5Te0.5) to 360 °C for Ge-rich Ge0.76Te0.24. The crystallized phase adopts the rhombohedral α-GeTe phase structure, and whatever the starting composition. For Ge-rich GeTe we observe a second characteristic temperature around 375 °C, which signs the crystallization of a precipitated cubic Ge phase and thus the presence of two distinct phases.