Composition, microstructure and SERS properties of titanium nitride thin film prepared via nitridation of sol–gel derived titania thin films

The titanium nitride thin film was successfully prepared via direct nitridation of the sol–gel derived TiO2 thin film at different temperatures in ammonia gas. The composition, microstructure and optical properties of the thin films were characterized in order to investigate their effect on the surface‐enhanced Raman scattering (SERS) performance of the thin films. With the nitridation temperatures increasing, the anatase phase transformed into titanium nitride phase in the films and the concentration of nitrogen incorporation increased accordingly. Consequentially, the sol–gel derived TiO2 thin film was converted to non‐stoichiometry titanium nitride (TiOxNy) thin film, as determined by X‐ray diffraction (XRD), RAMAN and X‐ray photoelectron spectroscopy (XPS). As a result, a blue‐shift of the surface plasmon resonance absorption peaks and narrowing optical band gap of the thin films were observed, leading to the improvement of SERS performance via electromagnetic enhancement mechanism and charge‐transfer effect. In addition, the surface of thin films became gradually rough with the nitridation temperatures increasing, ascribed to the growth of titanium nitride crystal grains. Most of all, the thin films nitrided at 1000 °C had the most rough surface, and many ‘hot spots’ formed on the thin film surface accordingly, which were favorable for enhancing SERS‐active, and thereby the thin films exhibited the largest SERS enhancement. Copyright © 2017 John Wiley & Sons, Ltd. The SERS spectra of Rhodamine 6G adsorbed on TiN thin film substrates indicate that SERS‐active of TiN thin films varies with different synthesis temperature. A blue‐shift of the surface plasmon resonance absorption peaks and narrowing optical band gap of the thin films were observed, leading to the improvement of SERS performance via electromagnetic enhancement mechanism and charge‐transfer effect. In addition, the suitable surface roughness and grain size in the TiN thin film were favorable to enhancing the SERS performance.