Surface morphology of lattice mismatched thin films

Abstract

In this work, we study a Solid-On-Solid (SOS) MBE growth model, for homoepitaxial growth, where atoms are dropped or deposited on randomly chosen lattice sites. Surface atoms may continue to hop at any time until they are buried by other atoms. We varied the substrate temperature and obtained the surface morphology and interface width (W). Our study shows that surface atoms do not hop much when the substrate temperature is low, resulting in a fast growing width. For higher temperature, the surface becomes kinetically rough that eventually turns into a layer-by-layer growth at very high temperature. We then expand this model to heteroepitaxial growth by including an effect of a strain caused by a lattice mismatch between the substrate and film materials and, namely Lattice Mismatch model. We find that the effect of strain leads to a mound formation when strain strength reach the critical value. For this work, the critical strength of strain should be between 0.8 and 1.2 eV while the critical thickness that lead to a mound formation should be between 1 and 2 ML. Moreover, our study shows that average mound radius depends onthe thickness and the substrate temperature. The average mound radius increases when thickness increases and exponentially increases when temperature increases. While the increase of strain strength does not effect the evolution of mound radius