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

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 °C) or from homogeneously formed nuclei (255-310 °C); both processes exhibited an identical activation energy of 200 kJ mol-1. At temperatures <230 °C, a Sb2O3 crystalline phase formed along the rhombohedral Sb2S3 structure. The normal growth model with the activation energy of ∼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 ξ 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.