A simple model for the growth of polycrystalline Si using the kinetic Monte Carlo simulation

摘要

An extension to the kinetic Monte Carlo simulation technique was developed in order to study thin film deposition and growth of a system approximating polycrystalline silicon. This method was developed to determine the effect of varying the angle of incidence of an atomic beam on the morphology of a poly-Si thin him grown on a crystalline Si substrate. This deposition procedure produced material comprised of individual grains, all with identical orientation; a first step towards modelling poly-Si. The addition of such grains does not significantly affect the bulk film properties relative to the single crystal case. The number of initial grains chosen to represent a set of pre-existing grains on the surface does not affect the gross morphology of the grown film once around 40 monolayers have been deposited. The chief advantage of this polycrystalline-like system is that it allows the observation of both columnar growth (at angles below about 65 degrees) and dendritic growth at angles above this value; growth of single crystalline material only shows the latter. This fact allows a comparison of results from atomic-scale simulation to existing theories that relate the angle of the morphological features of the grown film to the angle of the incident beam. We show that the simulation data are not particularly well represented by commonly used theories such as the tangent rule, or that due to Tait et al (1993 Thin Solid Films 226 196). Increased angles of incidence cause faster extinction of grains until a steady-state Value of the number of grains is reached. When gains are nucleated on a heterogeneous substrate, here chosen as a crude description of Si on glass, increased substrate temperature results in larger grains, and higher angles of incidence result in fewer nucleated grains due to non-local shadowing. [References: 15]