Diamond C 1s core-level excitons: surface sensitivity

The effect of surface termination on C 1s core-level bulk excitons found near the surface in single-crystal diamond is reported. By simultaneously recording bulk (total electron yield) and surface (partial electron yield) near-edge x-ray absorption fine-structure (NEXAFS) spectra with a range of single-crystal surface terminations, variable bulk exciton energy blueshifts and linewidth broadening were observed, most notably in the reconstructed single-crystal diamond. Investigation of polycrystalline diamond and ultrananocrystalline diamond films, using the same technique, allowed for a comparison between the reconstructed single-crystal diamond surface and nanodiamond bulk excitons. These findings suggest that surface-related effects can be misinterpreted as quantum confinement in some nanodiamond NEXAFS studies. Band bending is suggested as a possible contributor to these results.