Surface diffusion during decay of nano-island on Si(1 0 0) at high temperature

Surface diffusion during decay of a two-dimensional nano-island formed on Si(1 0 0) surface at 750-800 K is studied using STM and a kinetic Monte Carlo simulation. From a surface diffusion point of view, decay proceeds so that the total diffusion rate of atoms on a surface decreases. Atoms at step edges move more frequently than terrace atoms, which results in decay from step edges of the island. In addition, a terrace atom takes part in surface diffusion in the same way as an atom from steps of the island once it hops up on a terrace leaving a vacancy. The mass transport is not a specific atom process but terrace atoms and vacancies on the terrace are involved. Repeated upward and downward hops of atoms and their difference are combined with surface diffusion, which leads to the mass transport. Some tracks of atom using simulation show random walk with preferential diffusion along step edges, re-entering to the island, exchange of diffusing atom and filling in a vacancy on the terrace. The motion of the center of the island to the upper side of the terrace observed by STM is also well reproduced in the simulation.