Defect energy levels in Ta2 O5 and nitrogen-doped Ta2 O5

Crystalline Ta2 O5 has very rich defect energy levels as compared to the previously known ones. Thermal treatment of Ta2 O5 in a reducing atmosphere increases the photoluminescence (PL) intensity of the deep energy levels in the band gap as compared to the shallow ones. Nitrogen doping creates no new defect energy levels, but rather shifts the maximum PL intensity position of the deep energy levels to even deeper states. The doped nitrogen is interpreted to fill the oxygen vacancy at "in-plane" lattice sites when it is doped to Ta O6 octahedron.