Formation of finger-like step patterns on a Si(111) vicinal face

During deposition of Ga atoms, the structure of a Si(111) vicinal face is transformed from the 3×3 structure to the 6.3×6.3 structure. The transformation occurs preferentially from the lower side of steps. Since the density of Si atoms needed to form the 6.3×6.3 structure is lower than that to form the 3×3 structure, Si atoms are supplied onto the surface during the structural transition. The steps advance by incorporating the extra adatoms, and show a finger-like wandering pattern (H. Hibino, H. Kageshima, M. Uwaha, Surf. Sci. 602 (2008) 2421). To study the formation of the finger-like pattern, we carry out Monte Carlo simulations. When atoms are supplied immediately in front of a straight step, the step becomes unstable. Step wandering occurs and a step shows a finger-like pattern. The characteristic period of the fingers is consistent with the linear stability analysis and proportional to (β˜/V)1/2, where β˜ is the step stiffness and V is the step velocity (deposition rate).