Activation energy and its fluctuations at grain boundaries of Er3+:BaTiO3 perovskite thin films: Effect of doping concentration and annealing temperature

Abstract

An improved understanding of the grain growth kinetics in Erbium-doped Barium Titanate (BTE), has attracted great interest in its applications in photonic and electronic devices. To study the effects of doping and thermal treatment on the physical properties of films, the chemical surface, structural phase, grain size and fluctuations of the grain boundary of BTE films were analyzed and then their effects on the activation energy of the grain growth of the BTE films were revealed. BTE thin films were deposited on Si(100) substrates by electron beam physical vapor deposition (EB-PVD). XRD pattern analysis of the BTE films revealed a tetragonal crystal structure. Williamson–Hall analysis was used to confirm the tensile strain of the BTE thin films. The experimental results indicate that the Er doping in BaTiO3 show strong response by increasing the activation energy of the grain growth and increasing the grain size of the BTE films, while fluctuations of the surface roughness of the BTE films from 0.47 nm to 24.80 nm were also observed. Thin films: BTE2, BTE3, and BTE6 exhibit a grain growth exponent (n) of 5.71, 6.50, and 8.22 that respectively suggest a surface diffusion-controlled grain growth in these films. The activation energies for the grain growth came about 6.63, 6.95 and 19.7 kJ/mol for BTE2, BTE3 and BTE6, respectively, which were close to the values reported for the activation energy in BaTiO3. This was consistent with the high grain boundary density of the BTE films, which was responsible for the mechanism of surface diffusion and point defects. This behavior has been observed in case of BaTiO3, but for Erbium-doped barium titanate it has never been reported.