THEORY OF REFLECTANCE ANISOTROPY OF CLEAN AND HYDROGENATED (001)DIAMOND SURFACES

Density-functional theory is used to study the linear optical response of the (001) surface of diamond. The equilibrium atomic configuration s of the atomic structures are determined from fully converged self-co nsistent total energy calculations within the local density approximat ion. The electron-ion interaction is treated by using norm-conserving ab initio fully separable pseudopotentials in the Kleinman-Bylander fo rm. To account for the excitation aspect quasiparticle shifts are adde d to the single-particle energies; The influence of hydrogen adsorptio n is studied using a (2X2) translational symmetry. Optical transitions which involve surface states cause significant resonances in the refl ectivity in the visible and near ultraviolet ranges which exhibit a st rong polarization anisotropy. Adsorption of hydrogen strongly modifies the atomic structure and optical reflectance of the (001) diamond sur face.