Quantized electronic properties of diamond

Abstract

Diamond is a promising semiconductor which shows some unique surface electronic features if grown optimized with low bulk and surface defect densities. The appearance of a highly conducting surface layer, if immersed into electrolyte solution, is maybe the most striking feature. Scanning tunneling microscopy experiments on diamond in electrolyte solutions or covered by adsorbates are applied to determine the electronic properties governing these transitions. These experiments reveal the formation of unoccupied quantized electronic states in the valence band close to the surface. A two-dimensional density-of-state distribution with three levels from light-, heavy-, and split-off-band holes is detected. The formation of this system is the origin for the transformation of insulating diamond into a highly conductive film. Removal of the electrolyte causes a reversible transition into the insulating state and vice versa. No transformation can be detected on oxidized diamond surfaces which remains insulating.