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 L on the flux F during submonolayer epitaxy on Cu(100), the scaling exponent p in L is similar to F-p/2 is determined in the steady-state and island coalescence regimes. In both regimes at low temperature (223 K), a crossover of 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), p is 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.