Surface diffusion and formation for an ordered phase was investigated using the lattice gas model in Monte Carlo simulation. Interaction up to the second-nearest neighbor between particles was considered. The coverage was calculated as a function of a normalized coordinate by the square root of the diffusion time, starting from the initial step coverage. When the temperature T was lower than Tc, a shoulder appears in the coverage curve at near half coverage. It was shown that this shoulder corresponds to the formation of a c(2 x 2) phase, in which the existence of long range order was confirmed. On the other hand, when T was higher than Tc, the shoulder in the coverage curve disappears, but the short range order of the first and second nearest neighbor correlation still remains and the formation of islands of c(2 x 2) pattern was locally observed. The microscopic growth mechanism of the c(2 x 2) phase was considered. The observed growth rate was explained phenomenologically through the diffusion coefficient which was concentration-dependent.

Surface Diffusion and Formation of Ordered State. A.Natori, H.Ohtsubo: Surface Science, 1986, 171[1], 13-44