Martin Körner, Mario Einax, Philipp Maass
The capture numbers entering the mean-field rate equations (MFRE) for submonolayer film growth are determined from extensive kinetic Monte Carlo (KMC) simulations for simple representative growth models yielding point, compact, and fractal island morphologies. The full dependence of the capture numbers on island size, and on both the coverage and the D/F ratio between the adatom diffusion coefficient D and deposition rate F is determined. Based on this information, the MFRE are solved to give the MFRE island size distribution (MFRE-ISD). Results from applying the self-consistent (SC) theory for the capture numbers are found to deviate strongly from the KMC results. In light of this, it is surprising that the known good prediction of the adatom and island density is achieved by the SC theory. The MFRE-ISDs are shown to agree well with the corresponding KMC-ISDs for all island morphologies. For compact morphologies, however, this agreement is only present for coverages smaller than about 5% due to a significantly increased coalescence rate compared to fractal morphologies. It is shown that the lower coalescence rate for fractal morphologies is caused by the fact that fingers of two approaching fractal islands typically first avoid each other, which subsequently leads to a screening effect and a slowing down of further growth of these fingers. As found earlier, the scaled KMC-ISDs as a function of scaled island size approach, for fixed coverage, a limiting curve for D/F going to infinity. Our findings provide evidence that the limiting curve is independent of the coverage for point islands, while the results for compact and fractal island morphologies indicate a dependence on the coverage.
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http://arxiv.org/abs/1205.6734
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