Structural and electronic properties of oxidized silicon-terminated diamond surface

The termination of diamond surfaces is crucial for enhancing structural stability and broadening potential applications. Silicon, recognized as a promising termination, has been chosen experimentally to saturate diamond surface, while the structural model remains unclear. In this study, we employed a crystal structure search method to identify five kinds of oxidized silicon-terminated diamond structures. Their stability and electronic properties are calculated through density functional theory calculations. The structures exhibit indirect bandgaps of 0.98 - 2.26 eV, while the Si4O4-(111) structure exhibits a metallic band structure caused by the unique coordination environment of the surface silicon atoms. Additionally, these structures demonstrate positive electron affinity values (0.52 - 1.32 eV), while the Si4O4-(110) structure possesses a negative electron affinity of -0.54 eV. These theoretical predictions provide valuable insights for future experimental studies of diamond-based materials.