AVS 50th International Symposium
    Surface Science Wednesday Sessions
       Session SS-WeP

Paper SS-WeP27
Theory of Uptakes in Thin-film Growth: Autocatalytic-reaction Model and Kinetic Monte-Carlo Simulation

Wednesday, November 5, 2003, 11:00 am, Room Hall A-C

Session: Poster Session
Presenter: M. Suemitsu, Tohoku University, Japan
Authors: M. Suemitsu, Tohoku University, Japan
H. Togashi, Tohoku University, Japan
T. Abe, Tohoku Institute of Technology, Japan
Correspondent: Click to Email
In many thin film growth systems, the film grows via nucleation of 2D clusters, their growth, and coalescence. The process occurs with various time and space scales depending on the substrate temperature T and the impinging flux P of the precursors, which determines the uptake and morphology of the film. This T- and P-dependence arises from various T- and P-dependence of the surface processes behind the film growth: precursor adsorption and adatoms' migration and desorption. Migration and desorption are always thermally activated but with different activation energies. Adsorption may or may not be thermally activated but is consistently influenced by P. Reflecting this complication, thin film growth dynamics is a delicate function of both T and P. In high-P-low-T regime the growth proceeds with a random adsorption, which presents a Langmuir-type uptake of the film coverage. In low-P-high-T regime it proceeds with a 2D-island growth, which presents a sigmoid-function-type uptake. We have recently proposed autocatalytic-reaction (ACR) model as a rate equation for thin-film growth,@footnote 1@ which was successfully applied to various modes in dry oxidation at Si(001) up to one monolayer. With only two fitting parameters as it is, ACR bridges the gap between the two extremes of the behavior. To clarify the physics behind the model, we have conducted in this work a kinetic Monte Carlo (KMC) simulation assuming (1)adsorption of precursors only at the bare portion of the substrate, (2)finite residence time for the adatoms before desorption, (3)isotropic migration of adatoms, and (4)minimum stable clusters with two atoms. Quantitative agreement obtained between KMC and ACR allow us to discuss the development of the surface morphology using KMC. It was found that the success of the ACR model lies in its effective inclusion of nucleation, growth, and coalescence of adatoms. @FootnoteText@ @footnote 1@ M. Suemitsu, Y. Enta, Y. Miyanishi, N. Miyamoto, Phys. Rev. Lett. 82 (1999) 2334. .