Growth and coalescence in submonolayer homoepitaxy on Cu(100) studied with high-resolution low-energy electron diffraction.

By measuring the dependence of the island separation [ital L] on the flux [ital F] during submonolayer epitaxy on Cu(100), the scaling exponent [ital p] in [ital L][similar to][ital F][sup [minus][ital p]/2] is determined in the steady-state and island coalescence regimes. In both regimes at low temperature (223 K), a crossover of [ital p] is observed from a low-flux value of 1/3 to a high-flux value of 1/2. At elevated temperatures (263--305 K), [ital p][similar to]3/5 is obtained. These results agree with classic nucleation theories and recent Monte Carlo simulations, and imply that the smallest stable island changes directly to a tetramer from a low-temperature dimer with increasing temperature. Dissociation energy calculations using the embedded-atom method support these results.