High stability and photocatalytic activity of N-doped ZrO2 thin films

Abstract

Undoped and nitrogen-doped ZrO2 thin films were obtained by HiPIMS on ITO/glass substrates. To stabilize their structure, the films were subjected to a heat treatment. The properties of the heat-treated films (structure, morphology, elemental composition of the atomic species at the films surface, optical band gap, wettability and oxidation performance of Rhodamine B) were correlated. Some properties of the studied films were compared with the ones of the as-deposited films previously reported. By nitrogen doping, zirconia thin film modifies its fundamental absorption edge, becoming absorbent in the visible domain. The heat treatment improves the hydrophilic properties of both undoped and N-doped films, the last one becoming super-hydrophilic. The photocatalytic activity under UV was investigated for three RhB concentrations. The degradation efficiency is higher than 90 % for both undoped and N-doped ZrO2 films, being better for the N-doped film. The studied films are exceptionally stable, keeping their oxidation properties almost unchanged after five degradation cycles, with a special remark for the N-doped film (the degradation efficiency around 93 %). The role of ITO substrate in charge carriers separation was investigated, based on the allowed band edges values, determined both for the films and ITO.