ABSTRACTA review is presented in which existing theories of the formation of Schottky barriers are analyzed. The list includes macroscopic dielectric approaches and various microscopic quantum mechanical treatments. The central role of interface states and their different physical origins are assessed. Simple concepts, able to predict general trends in barrier heights, are examined along with detailed microscopic theories applied to individual contacts.
ABSTRACTThe electronic properties of TiO2 surfaces are of interest to further understanding of grain boundary effects in TiO2 and ZnO based varistor devices. Schottky barriers have been fabricated by Au or Al metallization on Nb doped TiO2-rutile [001] single crystal surfaces. Surface conditions included the presence or absence of either mechanical polishing induced surface defects and/or adsorbed oxygen. IV measurements on Au samples indicate that surface defects yield ohmic behavior, but the defects may be electrically compensated by adsorbed oxygen to give non-ohmic IV curves. All Al junctions show ohmic behavior which is interpreted in terms of reaction with surface oxygen. These results explain the necessity of firing varistor materials in an oxidizing atmosphere and suggest that the role of additives in these materials is to stabilize the oxygen concentration at the grain boundaries.
The role of quantum confinement in the formation of Schottky barriers in Pb–Si interfaces