In situ monitoring of stress change in GeTe thin films during thermal annealing and crystallization

Abstract

Stress changes in GeTe thin films on silicon have been studied in situ as a function of temperature by optical curvature measurements. Crystallization of the initially amorphous layers is evidenced by a steep tensile stress buildup. The crystallization temperature is shown to be thickness-dependent for the thinner films. Various annealing conditions, such as cooling/re-heating steps and isothermal stages, allow exploring the thermo-mechanical behavior of the films. A non-thermoelastic temperature-dependent behavior is observed in the amorphous phase before crystallization. Keywords: Phase-change materials, GeTe, Thin films, Stress measurements, Thermomechanical behaviour