Effects of mobility of small islands on growth in molecular-beam epitaxy

The effects of mobility of small islands on island growth in molecular-beam epitaxy are studied. It is shown that mobility of small islands affects both the scaling and morphology of islands during growth. Three microscopic models are considered, in which the critical island sizes are (Formula presented)=1, f2, and 3 (such that islands of size s⩽(Formula presented) are mobile, while islands of size s⩾(Formula presented)+1 are immobile). As (Formula presented) increases, islands become more compact, while the exponent γ, 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 (Formula presented). However, the prefactors provide a quantitative measure of the changing morphologies.