Visible Light Water Splitting via Oxidized TiN Thin Films

Thin films of TiN were prepared via RF magnetron reactive sputtering at various deposition pressures. The characteristics of the plasmas were measured by optical emission spectroscopy to optimize the conditions for the deposition of TiN coatings. After deposition, the thin films were annealed in a closed furnace at several different temperatures, and revealed the formation of different phases of TiO2. The resulting TiN/TiO2 thin films showed drastic changes in their crystal structure, optical properties, and photo-electrochemical performance. By examining how the deposition pressure and postdeposition annealing conditions affected the TiN film structure and performance, samples were prepared to optimize visible light absorption and activity. A model for the oxidation process was proposed which described the structural change from TiN to TiO2 through optical, morphological, and crystalline characterization. This study has systematically shown the ability to tailor the optical, crystalline, and photoactive properties of TiO2 by tailoring the intrinsic properties of TiN thin films and subsequent annealing. These results can be utilized for many solar driven optoelectronic devices.