Native crystal growth in 60 nm Sb2S3 amorphous film: A joint microscopy-calorimetry study

Abstract

Joint direct microscopy-calorimetry measurements of crystal growth were performed for a 60 nm amorphous Sb2S3 film deposited either on a Kapton foil or on a soda-lime glass. Calorimetric crystallization proceeded in two steps, originating either from mechanical and stress-induced defects (230-275 degrees C) or from homogeneously formed nuclei (255-310 degrees C); both processes exhibited an identical activation energy of 200 kJ mol(-1). At temperatures <230 degrees C, a Sb2O3 crystalline phase formed along the rhombohedral Sb2S3 structure. The normal growth model with the activation energy of similar to 250 kJ mol(-1) was used to describe the microscopic crystal growth rate data, and the viscosity-diffusivity decoupling was characterized by Ediger's parameter xi varying between 0.40 and 0.55. The crystal growth rate was slightly higher in the film deposited on the glass substrate, with the compressive stress introduced at higher T having only a small effect. Meanwhile, the deposition on the glass substrate led to a significantly higher (especially below the glass transition temperature) nucleation rate, which underlines the key aspect of the crystallization process in very thin chalcogenide films: the formation of nuclei due to the internal stresses arising from the difference of the film/substrate thermal expansion coefficients.