Atomic layer deposition of nitrogen-doped titanium dioxide films

Layers and nanostructures of titanium dioxide (TiO2) have found several practical applications for paints, sunscreens, protecting layers, photocatalysis, water splitting or photovoltaics. The applicability of this material depends on its crystalline phase. Among the three possible crystal structures of TiO2, anatase is commonly used for photocatalysis. TiO2 with anatase structure, however, can undergo transition to the rutile phase, which is accelerated by the heat treatment at temperatures between 450 and 1200 °C. In our work, we obtained undoped and nitrogen-doped titanium dioxide (TiO2:N) films, grown by atomic layer deposition, with a stable anatase structure. The as-grown amorphous films were deposited at 120 °C on single crystalline Si substrates. After deposition samples were annealed by flash lamp annealing for 20 ms in nitrogen ambient. Annealed films show anatase structure which is stable up to anneal temperatures close to the melting point of Si (< 1400 °C). This was confirmed by ?-Raman and x-ray diffraction studies. We analyze the anatase crystal structure of the annealed TiO2:N films as a function of the annealing energy density and the N concentration. The investigations are complemented by temperature-dependent photoluminescence measurements. The work was partially supported by the EU 7th Framework Programme project REGPOT-CT-2013-316014 (EAgLE).