Electronic structure of δ-Ta2O5 with oxygen vacancy: ab initio calculations and comparison with experiment

Electronic structure of oxygen vacancies in Ta2O5 have been studied theoretically by first-principles calculations and experimentally by x-ray photoelectron spectroscopy. Calculations of delta-Ta2O5 were performed using density functional theory within gradient-corrected approximation with the +U approach. Results indicate that the oxygen vacancy causes a defect level in the energy gap at 1.2 eV above the top of the valence band. To produce oxygen vacancies, amorphous films of Ta2O5 were bombarded with Ar+ ions. XPS results indicate that the Ar-ion bombardment leads to the generation of the oxygen vacancies in Ta2O5 that characterize the peak at 2 eV above the valence band. The calculated spectrum of crystalline delta-Ta2O5 demonstrates qualitative correspondence with the XPS spectrum of the amorphous Ta2O5 film after Ar-ion bombardment. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3606416]