Factors Influencing Hydroxyl Radical Formation in a Photo-Induced Confined Etching System

In this paper, we studied the formation of free OH on a TiO2nanotube array electrode in a photo-induced confined etching system. We used fluorescence spectroscopy, transient photocurrent response, electrochemical impedance spectroscopy(EIS), and Mott- Schottky analysis to investigate the influence of several key factors, including the applied potential, the illumination time, and the pH value. The highest efficiency for the photoelectrocatalytic formation of free OH on the TiO2nanotube array electrode was achieved at an applied potential of 1.0 V(vs a saturated calomel electrode(SCE)); the photoelectrocatalytic generation and consumption of free OH quickly approached a steady state in this system, as the confined etching layer formed by OH remained stable during illumination. This may allow good control of the etching precision during continuous etching processes. The highest efficiency for the photoelectrocatalytic formation of free OH on the TiO2nanotube array electrode was observed at pH 10. The results have an important significance for regulating and optimizing photo-induced confined etching system, which can be used to improve the etching speed or the leveling precision during the planarization of copper.