Theoretical analysis of the energy levels induced by oxygen vacancies and the doping process (Co, Cu and Zn) on SnO2 (110) surface models

Density functional calculation at B3LYP level was employed to study the sur face oxygen vacancies and the doping process of Co, Cu and Zn on SnO2 (110) surface models. Large clusters, based on (SnO2)(15) models, were selected to simulate the oxidized (Sn15O30), half-reduced (Sn15O29) and the reduced (Sn15O28) surfaces. The doping process was considered on the reduced surfac es: Sn13Co2O28, Sn13Cu2O28 and Sn13Zn2O28. The results are analyzed and dis cussed based on a calculation of the energy levels along the bulk band gap region, determined by a projection of the monoelectron level structure on t o the atomic basis set and by the density of states. This procedure enables one to distinguish the states coming from the bulk, the oxygen vacancies a nd the doping process, On passing from an oxidized to a reduced surface, mi ssing bridge oxygen atoms generate electronic levels along the band gap reg ion, associated with 5s/5p of four-/five-fold Sn and 2p of in-plane O cente rs located on the exposed surface, which is in agreement with previous theo retical and experimental investigations. The formation energy of one and tw o oxygen vacancies is 3.0 and 3.9 eV, respectively. (C) 2001 Elsevier Scien ce B.V. All rights reserved.