Density Functional Theory Study on Mechanism for Oxygen Diffusion in Silicon with Hydrogen

An atomistic mechanism is proposed that why hydrogen enhances oxygen diffusion in silicon. We combine the ab initio molecular dynamics simulation metadynamics (AIMD-MetaD) and nudged elastic band calculation to study the migration of a single O atom with H atom in silicon. The migration paths of O and H are obtained by density functional theory calculation. The barrier of minimum energy path, which is 1.87eV, is 0.7eV lower than the energy barrier of O atom in bulk silicon. This ab initio calculation elucidates how H atom moving in silicon, which explains why the wet oxidation rate is faster than dry oxidation. AIMD-MetaD allow us to accurately learn the free-energy landscape to understand the motion of atoms during wet oxidation, which has rarely been mentioned in past studies.