Effects of miscut substates on surface morphology of thin film simulated by DAS sarma-tamborenea model

Abstract

The Das Sarma-Tamborenea (DT) model is a model used to study molecular beam epitaxy (MBE) thin film growth process. In MBE simulations, atomic diffusion follows Arrhenius hopping probability which depends on number of nearest-neighbor bonds and substrate temperature. The DT model simplifies this and uses only bond counting in the diffusion process. Substrate temperature can be varied via the change in the diffusion length. In the thesis, the DT model with long surface diffusion length is used to study thin film growth on miscut substrates. It is found that the change in the diffusion length is not clearly seen in the simulated film, which disagrees with experimental results. We modified the diffusion rule of the DT model by increasing the mobility of atoms and results from the modified DT model agree with experiments. First, using the modified DT model to study effects of surface diffusion length (L [subscript d]) on the miscut substrate as the terrace width (L [subscript t]) and the step height (s) is fixed, we found that the film can maintain the initial tilt angle for a long time when iota [subscript d]is more than or equal to L [subscript t]). Seconds, the effects of the initial configuration of miscut substrate is studied. The first case, the terrace width is varied and step height is fixed at 1 sites, we found that the initial pattern can survive for a long period of time when L [subscript 1] is less than or equal to iota [subscript d] In the second case, the step height is varied and the terrace width is fixed at L [subscript t] = iota [subscript d], we found that s > 1 induces roughness on the film surface confirmed by the rapidly decreasing persistence probability.