The local atomic environment of lattice vacancies in the monoxide was studied, using positron annihilation techniques, for compositions ranging from TiO0.74 to TiO1.26. In non-stoichiometric material, a high concentration of vacancies was suggested to exist on both the Ti and the O sub-lattices. From an analysis of the core electron momentum distribution of the atoms surrounding the vacancies in disordered, as well as in ordered, material, O atoms were deduced to make up the local vacancy environment; indicating that positrons were trapped by Ti- and not by O-vacancies. Positron lifetime measurements showed that a decrease in the O content, and a disordering process in non-stoichiometric material, were accompanied by an increase in the valence-electron density on the Ti vacancy.

Vacancies on the Ti Sublattice in Titanium Monoxide TiOy Studied using Positron Annihilation Techniques. Valeeva, A.A., Rempel, A.A., Sprengel, W., Schaefer, H.E.: Physical Review B, 2007, 75[9], 094107