ISLAND SIZE AND ENVIRONMENT DEPENDENCE OF ADATOM CAPTURE - CU CO ISLANDS ON RU(0001)/

We quantify the rate of capture by Co islands on Ru(0001) of additiona lly deposited Cu atoms, using scanning tunneling microscopy. The depen dence of the capture rates on Go-island size is shown to reflect large r island-free areas surrounding bigger islands, a feature neglected in mean-field treatments. We also find a strong direction dependence in Cu adatom capture, reflecting the local environment of individual isla nds. These features are elucidated by simulations and diffusion equati on analyses.