Effects of island-edge exchange barrier on 2D pattern formation in surfactant-mediated epitaxy

The nucleation and growth of two-dimensional islands in a surfactant-mediat ed epitaxy system have been studied by computer simulation. To improve the recent results published in the literature, we use a configuration-dependen t energy barrier for the exchange process at the island edge in our model. The simulations produce fractal islands at high temperatures or low deposit ion fluxes, and a transition to regular compact islands occurs at lower tem peratures or higher fluxes, in good agreement with the recent experimental results. The barrier for the island-edge exchange has quite a strong effect on the island density as a function of temperature and flux. A small chang e of the island-edge exchange barrier induces a large variation of the isla nd density in the low-temperature or high-flux region. The flux-dependent i sland density shows a clear scaling-law behaviour in the intermediate-flux region. The scaling exponent increases evidently as the island-edge exchang e barrier increases.