A kinetic Monte Carlo simulation of fiber texture formation during thin-film deposition

Abstract

A modified kinetic Monte Carlo computer simulation has been developed and applied to the investigation of fiber (out-of-plane) texture formation in polycrystalline thin films grown in the absence of high-energy bombarding particles. Unlike high-energy deposition, in which texture formation appears to result from a combination of preferential resputtering and self-shadowing at the film surface, the simulation results described herein indicate that texture formation in low-energy deposition is caused by a bias in surface diffusion and adsorption energies on different crystallographic faces. A net flux of atoms toward grains with high-binding-energy faces oriented along the film surface coupled with a greater probability that an atom near the interface between two grains will become attached to the high-binding-energy face produces a preferential in-plane expansion of these grains at the expense of their neighbors. The rate of texture development is shown to increase with increases in the binding energy of the preferred faces and the deposition temperature, and to decrease with increasing deposition rate and initial grain size. Voids and vacancies incorporated into the film form as a result of incomplete layer-by-layer growth induced by conditions of low surface diffusion and high deposition rate. The density of voids and vacancies, as well as the local surface roughness, varies from grain to grain within the material due to the differences in surface diffusion on the crystallographic faces exposed to the deposition flux as each layer of the various grains is formed.