Effects of Small Island Mobility on Growth in Molecular Beam Epitaxy

TL;DR

This study investigates how the mobility of small islands influences the growth, morphology, and scaling behavior in molecular beam epitaxy, revealing that increased island mobility leads to more compact islands and altered growth dynamics.

Contribution

It introduces three microscopic models with different critical island sizes to analyze the impact of small island mobility on growth and morphology in molecular beam epitaxy.

Findings

Increased island mobility results in more compact island structures.

The island density exponent $b3$ increases with higher critical island size.

Fractal dimensions remain largely unaffected by changes in island mobility.

Abstract

The effects of mobility of small islands on island growth in molecular beam epitaxy are studied. It is shown that small island mobility affects both the scaling and morphology of islands during growth. Three microscopic models are considered, in which the critical island sizes are $i^*=1,2$ and 3 (such that islands of size $s \le i^*$ are mobile while islands of size $s \ge i^{\ast}+1$ are immobile). As i^* increases, islands become more compact, while the exponent $\gamma$ which relates the island density to deposition rate increases. The morphological changes are quantified by using fractal analysis. It is shown that the fractal dimensions are rather insensitive to changes in i^*. However, the prefactors provide a quantitative measure of the changing morphologies.