Monte Carlo simulation of the growth of SrTiO3 thin film with molecular source

A three-dimensional model of SrTiO3 thin film growth under ultraslow growth rate was proposed based on Monte Carlo method. The model is based on Solid on Solid (SOS) model with periodic boundary condition. The ideal molecular source is regarded as a mixture of predominantly SrTiO3 molecules and a few SrO and TiO2 molecules. Monte Carlo events consist of deposition, diffusion of molecules and generation of SrTiO3 molecules. The results show that in the temperature range simulated, the binding possibility of SrO and TiO2 to SrTiO3 increases with the increase of the substrate temperature, resulting in the decrease of the number of SrO and TiO2 molecules. When the substrates temperature reaches a special value (<800 K), all SrO and TiO2 molecules may already convert to SrTiO3, which agrees with our previous experiment. Thus, under ultraslow deposition rate and at the temperature beyond 800 K, a simplified Monte Carlo model consisting only of SrTiO3 cell diffusion can be achieved. The dependence of morphology on the temperature is simulated and the results show that under ultraslow deposition rate, the SrTiO3 thin film grows with layer-by-layer mode at higher temperature and with island mode at lower temperature, which is qualitatively consistent with the experiment.