Electronic structure of the surface of ruthenium — titanium oxide anodes. X-ray electron and modulation spectroscopy

Abstract

Ruthenium — titanium oxide films of various composition have been studied by a high resolution electron microscopy method. X-ray electron spectroscopy and electroreflection. It is shown that the composition of the films is non-uniform because of the presence of the ruthenium oxide phase in the form of small particles (5–30 nm) dispersed in the TiO 2. As a result of the interaction of these particles with the defective sections of the TiO 2 phase, an impurity (contact) band is formed inside the latter. Such contact microareas have an energy gap less than in TiO 2. It is this microheterogeneous structure (and consequently the spottiness of the film surface) that determines the electronic properties of the films. Potential barriers of different amplitudes are formed in films with a composition below the critical ( x c < 30 mol.% RuO 2) at the interface between the contact microareas or TiO 2 and the ruthenium oxide particles. It is these barriers that determine the surface band structure of these films and are responsible for the two observed flat — band potentials being considerably different from the TiO 2 one. When the critical concentration is achieved, the barriers disappear and the Fermi level of the films drops into the contact band, which brings together the ruthenium oxide particles (they form an infinite conductive cluster).