Electron paramagnetic resonance was used to identify photo-induced titaniumassociated

electron traps in TiO2 crystals (rutile). Defect production occurred at

low temperature with 442nm laser light. Spectra with S = 1/2 and S = 1 were

assigned to singly ionized and neutral oxygen vacancies, respectively. These

oxygen vacancies have their unpaired spins localized on the two neighbouring

titanium ions aligned along the c axis. A Ti3+ ion next to a Si4+ ion, a Ti3+ selftrapped

electron, and a self-trapped hole shared by two adjacent oxygen ions were

also observed. Isolated substitutional Fe3+ and Cr3+ ions serve as hole traps.

Photo-Induced Electron Paramagnetic Resonance Study of Electron Traps in TiO2

Crystals: Oxygen Vacancies and Ti3+ Ions. S.Yang, L.E.Halliburton,

A.Manivannan, P.H.Bunton, D.B.Baker, M.Klemm, S.Horn, A.Fujishima: Applied

Physics Letters, 2009, 94[16], 162114