Preparation of Co:TiO2 thin films by crossed-beam pulsed laser deposition

Co:TiO2 thin films were deposited using two interacting plasmas produced from different targets, TiO2 and cobalt. By keeping constant the laser ablation conditions on the TiO2 target and changing them on the Co target, it was possible to vary in a controlled way the Co content in the films. The cobalt plasma parameters, such as the ion kinetic energy and plasma density, were determined for each deposition condition in an attempt to correlate them with the material’s properties. The cobalt ion mean kinetic energy was varied from 36 to 789 eV, resulting in films with Co content from 1.2 up to 5.1 at.%, respectively, revealing that the cobalt content can be controlled by the Co+ kinetic energy. The study of the optical properties showed that the optical band gap decreased from 2.9 to 2.0 eV as the Co content increased. Raman spectroscopy was used to characterize the microstructure of the deposits, and the obtained results suggest the formation of two coexisting phases: TiO2 in its rutile phase and CoTiO3. It was found that as the Co+ energy increases, the CoTiO3 phase develops in a greater quantity. XPS measurements confirm the Raman spectroscopy results.