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Molecular oxygen as charge-compensating and magnetic centers in anatase Ti O2

Lookup NU author(s): Professor James DawsonORCiD

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Abstract

© 2015 American Physical Society.Titanium dioxide is an important material that has found applications in various fields of technology. Many of its functionalities originate from intrinsic defects. In this paper, by using state-of-the-art hybrid density-functional calculations, a defect structure associated with the Ti vacancy in anatase TiO2 is identified. This structure is significantly more stable than the existing model and accounts for experimental observations. We find that the four electron holes resulting from a Ti vacancy are self-compensated by the formation of a dioxygen molecule O2 from two lattice oxygen anions O2-. The oxygen molecule has a triplet-spin S=1 electronic state and, hence, can be the source of local magnetic moments observed experimentally in undoped samples. In addition to the typical idea of cation vacancies being acceptor-type defects that can accept electrons, we find that the Ti vacancy can actually accommodate extra holes (lose electrons) by forming another oxygen molecule and, therefore, also behave as a donorlike defect (or a hyperdeep donor). Furthermore, the presence of the Ti vacancy causes an up-shift of the electronic states of the neighboring oxygen anions, which can account for a unique feature in the optical absorption spectrum of "yellow" anatase TiO2.

Publication metadata

Author(s): Chen H, Dawson JA

Publication type: Article

Publication status: Published

Journal: Physical Review Applied

Year: 2015

Volume: 3

Issue: 6

Print publication date: 18/06/2015

Online publication date: 18/06/2015

Acceptance date: 01/01/1900

ISSN (electronic): 2331-7019

Publisher: American Physical Society

URL: https://doi.org/10.1103/PhysRevApplied.3.064011

DOI: 10.1103/PhysRevApplied.3.064011

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