The interaction of ions and easily ionized species with oxide surfaces as studied by tunneling spectroscopy

The thin film properties of alumina and magnesia, the substrates most frequently used in tunneling spectroscopy, are reviewed. The composite barriers, Al₂O₃/SiHO_x and Al_xSO_y are also discussed. Tunneling studies provide information about absorbate-surface interactions; weak counterion adsorption effects through very strong direct chemical modifications can be studied. Tunneling studies of anionic transition metal complexes adsorbed on alumina provide significantly more information about the nature of the surface species than corresponding IR studies. The adsorption of TCNE on alumina from solution is used to exemplify how tunneling spectroscopy may be integrated into a manifold of conventional techniques (IR, ESR, and elution studies in this case).