We studied resistance changes in TiOx films, induced by annealing and voltage applications. X-ray diffraction (XRD) results showed that annealing TiOx at temperatures in the range of 300 to 650 degrees C caused crystal structure changes. After 650 degrees C anneal, TiOx showed rutile TiO2 XRD peaks. In addition to the XRD changes, 650 degrees C annealing in air changed electrically conducting TiOx to a perfect insulator. We think that the emergence of rutile XRD peaks and the resistivity increase are correlated. When sufficiently high voltage was applied to TiOx, current started to decrease, which was an indication of oxidation of TiOx. After cool-down, we confirmed that resistance was increased by the applied voltage. We explain that the resistance increase is due to an oxidation of a conducting TiO into an insulating TiO2. This method can be used to write data in memory devices, where different resistance values represent stored data. (C) 2008 Elsevier B.V. All rights reserved.