Optical Absorbance and Photoelectrochemical Quantum Efficiency of Titanium Oxide Modified by Ion Implantation and Reductive/Oxidative Annealing

Abstract

AbstractWe report on the optical absorbance A and the photoelectrochemical quantum efficiency η of Titanium oxide samples modified by ion implantation and reductive/oxidative annealing. Rutherford‐Backscattering spectra were taken to probe the depth profile of implanted Kr+. It is shown that A varies drastically upon modification. Generally, with increasing Ti/O ratios the absorbance decreases. The observed decrease in A upon implantation of stoichiometric TiO2 is attributed to an increase of the Ti/O ratio. The suggested explanation takes into account the formation of Ti3+ ‐ O vacancy complexes which influence the electronic structure of TiO2. Furthermore it is shown that changes of A give rise to conductivity changes. This reflects changes in ND, the doping density, εr, the relative dielectric constant, and lp, the mean free diffusion length of minority carriers. The observed photoelectrochemical quantum efficiency η of modified samples is discussed in terms of model calculations which take into account changes of ND, εr, lp and the absorption coefficient α. Recombination losses of photo‐produced electron‐hole‐pairs via band gap states introduced by the implanted ions are also discussed.