Photoemission studies of the electronic properties of the space charge layer of SnO₂(110) surface

The electronic properties of the space charge layer of the SnO₂(110) surface are fundamental for modelling of the sensing properties of SnO₂-based gas sensors. Up to now it was mainly studied by photoemission techniques and there are many experimental data in the literature concerning the electronic properties of the space charge layer of the clean SnO₂(110) surface, combined with AES, ISS,XPS data on surface chemistry and LEED data on atomic structure. However, most of them concern only the variations of the work function Φ and / or surface potential Vs (surface band bending eVs) after sputtering, sputtering-annealing, and different types of oxidation, together with distribution of the valence band electronic states. In this paper a critical analysis of the electronic properties of the space charge layer of the SnO₂(110) surface determined in the recent XPS and UPS stidieds is presented. Special attention was given to the correlations between surface chemistry (composition and atomic structure) and the work function Φ, surface band bending eVs and interface Fermi level position Ev - Ef in the band gap, together with the distribution and origin of the filled defect electronic band gap states.