Boron-terminated diamond (100) surfaces with promising structural and electronic properties
Boron (B) termination plays an important role in determining the surface properties of diamond (100) surface. A recent study [J. Mater. Chem. C 2019, 7, 9756] reported a stable surface structure with one B atom per carbon atom based on the high-symmetry adsorption sites having novel electron affinity (EA) property. In this work, using global structure prediction method and first-principle calculations, four kinds of B-diamond (100) surfaces with 0.5 monolayer (0.5 ML, one B atom per two carbon atoms), and 1 ML-α, 1 ML-β, and 1 ML-γ (one B atom per carbon atom with three types of configurations as α, β, and γ) coverages obtained are dynamically and thermally stable. The calculations reveal that B termination effectively modulates the EA of diamond (100) surface. The 0.5 ML coverage has a small positive EA of 0.24 eV, while the latter three 1 ML coverages with different configurations possess the negative EA of 1.27, 1.25, and 0.76 eV, respectively, due to the difference in charge accumulation and surface dipole moment. Moreover, the B-related surface states are introduced into the bandgap of bulk diamond, and the band dispersions of the surface states are small (large) in 0.5 ML and 1 ML-γ (1 ML-α and 1 ML-β) as a consequence of the different arrangements of B atoms and the bond lengths between B atoms on the surface. Our finding provides a theoretical guidance for the design and fabrication of B-diamond-based electronic devices.