Adatom Diffusion during Decay of 2D Island on Si(100) Studied by Kinetic Monte Carlo Simulation.

Abstract

Adatom diffusion process during decay of a 2D island formed on Si(100)-2×1 surface is analyzed using a kinetic Monte Carlo simulation based on a solid-on-solid model. The diffusion is basically a mass transport on the surface; both a source and a drain of adatoms are needed. The experimental results of the decay process of a 2D island at the substrate temperature around 800 K are reproduced when a boundary condition with proper drains is adopted in the system of simulation. The decay rate depends on the boundary condition. The decay is governed by adatom diffusion process, but the process is not so simple. An adatom does not move long distance on a flat terrace. It is trapped by a vacancy created by hopping of another atom from the terrace, and the latter atom moves on the terrace instead of the former in the next step. This vacancy mediated diffusion of adatom is a key issue for understanding diffusion process on surface, especially at high temperature.