Comparison of oxygen vacancy defects in crystalline and amorphous Ta2O5

Abstract

The structure, formation energy and energy levels of the oxygen vacancies in crystalline and amorphous Ta2O5 have been calculated by first principle methods. In the crystalline phase, the 2-fold coordinated intra-layer vacancy is the lowest cost vacancy, and forms a deep level 1.5eV below the conduction band edge. The 3-fold intra-layer vacancy and the 2-fold inter-layer vacancy are higher cost defects, and form shallower levels. In the amorphous phase, the lower density results in higher concentration of inter-layer like 2-fold O coordination. The O vacancy diffusion barrier is 0.1–0.3eV in both cases.