Application of Regional Chemical Potential Analysis to Si Adsorption on the Diamond (001) Surface

Abstract

Adsorption of carbon dimers and Si atoms on the reconstructed diamond (001) surface is inves- tigated using density functional theory and regional chemical potential (RCP) analysis. We first demonstrate that the RCP distribution provides a real-space description of the bonding rearrange- ments responsible for the site-selective growth of experimentally observed carbon-dimer ribbons. We then examine the adsorption of single and multiple Si atoms. The calculated adsorption ener- gies show that a single Si atom preferentially bridges a surface carbon dimer and that subsequently adsorbed Si atoms favor neighboring dimer sites through Si-Si bond formation. The RCP analysis identifies electron-donating regions at the ends of finite Si chains, providing an intuitive explanation for their preferential one-dimensional growth and a physically motivated strategy for selecting candi- date adsorption structures. At higher Si coverages, geometry optimizations yield Si stripe and planar square-lattice structures on the diamond surface. Surface phase analysis indicates that an increase in the effective Si chemical potential favors structures with progressively higher Si coverages, from the Si stripe phase to the Si square-lattice phase. The calculated band structures reveal a progressive reduction of the surface band gap with increasing Si coverage. In the Si square-lattice structure, several bands cross the Fermi level, and the conducting states along the two in-plane directions have distinct Si and C character because the underlying diamond (001) substrate lacks fourfold rotational symmetry. These results establish RCP analysis as a useful approach for interpreting surface covalent bonding and guiding the exploration of adsorption-driven surface structures.