Competitive etching and oxidation of vicinal Si(100) surfaces

Exposure of a vicinal Si(100) surface to oxygen at around 550 C produces etching-mediated step recession. In addition, some oxide islands are formed which locally pin receding steps. We develop an atomistic lattice-gas model for this process which accounts for the interplay between oxygen surface chemistry (adsorption, diffusion, oxide formation, and etching via SiO desorption) and the silicon surface and step dynamics (anisotropic diffusion and aggregation of di-vacancies formed by etching, and ad-dimer attachment-detachment dynamics at steps incorporating anisotropic energetics). Kinetic Monte Carlo simulation of this model produces step morphologies retaining some qualitative but not quantitative features of their equilibrium structure (alternating rough S _B steps and smooth S_A steps), except for pinning which produces protruding "fingers". These features are seen in Scanning Tunneling Microscopy studies.