A mechanism for SiCl2 formation and desorption in the etching of Si(100 - (2 × 1) at low chlorine coverages is analyzed using first-principles calculations. We find that the two monochlorinated Si atoms of a surface dimer can rearrange into a metastable SiCl2(a) adsorbed species plus a Cl-free Si atom. Desorption of SiCl2 occurs via a two-step mechanism, in which the adsorbed species is preliminarily stabilized by the diffusion away of the free Si atom. The energy barrier to form SiCl2(a) is lower on a dimer next to a dimer vacancy than in an undamaged region of the surface, consistent with recent STM observation of preferential linear growth of etch pits along dimer rows.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)