Surface electronic structure of oxides as established by thermally stimulated electron current measurements

Abstract

Adsorption and catalysis at the surface of metal oxides is directly related to the electronic constitution in the vicinity of the surface not merely in terms of the predominant electronic character but more importantly the complex assembly of trapping electronic states. Experimental techniques have been developed using both thermally stimulated electron current measurements and thermal glow curves to establish in detail the complex distribution of electronic states. They can lead to quantitative information on both the position and occupancy of trapping states. Preliminary correlation has also been established between trapping states and simple adsorption phenomena. Detailed characteristics have been established for various samples of very high purity zinc oxide and TiO₂ including a study of the effect of controlled impurities at a level of a few p.p.m. and variations due to particle size. Direct correlation is made with the adsorption of gases, simple catalytic reactions, the interaction with binders used in electron photography and general characteristics of electron photographic coatings.