Tight-binding study of hydrogen on the C(111), C(100), and C(110) diamond surfaces

Abstract

The band structure, total energies, and relaxed geometries are calculated for the C(111), C(100), and C(110) surfaces using a parametrized tight-binding model for carbon. The method and addition of C-H parameters to the model are described in detail. Results for the bare and hydrogenated C(111) surfaces are used to compare the accuracy of the method with ab initio techniques. A stable hydrogenated (2×1) π reconstructed surface is found, which resembles the C(110) surface. Removal of one H atom from the dihydride C(100) results in a 3/2 hydride surface, where the odd hydrogen is bonded equally to two surface carbons. Although the fully H-covered C(100)(2×1) surface has a clean gap, the partially covered surface has a half-filled state, consistent with photoemission data. The geometries and H vibrations are also presented for the C(110) surface. The surface chains on the bare C(110) have bond lengths close to graphite and dimerize from a Peierls distortion. Addition of H to this surface restores the bond lengths to approximately that of bulk diamond. Comparison of the band structures and H vibrations with experiment helps identify the nature of the hydrogen coverage on the surfaces.