Improving HER and OER reactions by tailoring oxidation reactions during pulsed laser deposition of TiON thin films

Control over the gas-phase oxidation reaction during pulsed laser deposition (PLD) of 150 nm TiN films under varying O₂ atmospheres was achieved by tailoring surface oxidation states which showed a good potential for rare-metal-free water splitting. An optimum for the nitrogen occupation was found at 0.1 Pa O 2 , which corresponds to the highest deposition energies during film growth. Additionally, the increase in deposition temperature up to allows a better incorporation of nitrogen up to a value of 2.5. The deposition process was monitored via angle- and time-resolved Langmuir probe measurements combined with optical emission spectroscopy. Under residual atmosphere conditions, high kinetic ion energy which reached 1.8 keV facilitated both gas‒phase oxidation and thermal oxidation of the films. In the intermediate pressure regime, where energies where in the range of hundreds of eV, the formation of suboxides and fractional nitrides was observed, with the transition towards TiO₂ driven by increased plasma ion acceleration and increased ion density by a factor of 1.2. The integration of advanced plasma diagnostics with thin-film analysis provides a deeper understanding of the oxidation dynamics in PLD, offering valuable insights for tailoring the properties of oxynitride thin films.