Crystallization and surface morphology evolution of erbium fluoride films on different substrates

Erbium fluoride (ErF3) films were thermally deposited on Ge(1 1 1), Si(0 0 1) and copper mesh grid with different substrate temperature. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize the structure and morphology of the films. The structure of ErF3 films deposited on germanium and silicon changed from amorphous to crystalline with increasing the substrate temperature, while the crystallization temperature of the films on silicon is higher than that of on germanium. The infrared optical properties of the films change greatly with the evolution of crystal structure. It is also found that the morphology of ErF3 film on Ge(1 1 1) at 200 °C is modulated by the stress between the substrate and film. The SEM and TEM results confirmed that the ErF3 films on copper mesh grid were crystalline even at 100 °C. Interestingly, the ErF3 films show flower-like surface morphology when deposited on copper mesh at 200 °C. The crystallization temperature (Tc) of ErF3 films on the three substrates has the relation which is Tccopper