O xygen vacancy defects in tantalum pentoxide : a density functional study

First principles total energy calculations were performed in order to characterize O vacancy defects in Ta O . A simplified 2 5 version of the crystalline orthorhombic phase of Ta O was used in this study. Results indicate that O vacancies in Ta O 2 5 2 5 can be broadly classified based on their location in the lattice. One type of vacancy (occupying the ‘in-plane’ sites) displays deep or mid gap occupied states, and shallow unoccupied states, while a second type (occupying ‘cap’ sites) results in shallow occupied states. For a wide range of local Fermi level or chemical potential, the neutral and 12 charged states of the in-plane type vacancy and the 12 charge state of the cap type vacancy are found to be most stable.  2003 Elsevier B.V. All rights reserved.