Preparation and characterisation of chromium-doped cobalt oxide spinel thin films

Thin films of cobalt-based oxide spinel were prepared by pulsed spray evaporation chemical vapour deposition (PSE-CVD), and doping with chromium was systematically investigated up to a Cr/Co ratio of 0.096, corresponding to a stoichiometry of Co3-xCrxO4 with x = 0.00-0.26. The effect of doping concentration on the structure, assessed by X-ray diffraction and Raman scattering, and on the optical and electrical properties of the oxide films was investigated. Single-phase spinel could be preserved for stoichiometries below x = 0.22. The influence of Cr-doping on the band gap energies and on the electrical conductivity was determined, and the obtained results were exploited to discuss the cationic site occupations. The influence of Cr doping was complemented by the investigation of the surface catalytic reactivity towards the oxidation of dichloromethane.