Intensity-modulated photocurrent spectroscopy of thin anodic films on titanium

Photoelectrochemical techniques have been applied in order to elucidate optical and electronic properties of thin anodic films on titanium in sulphuric acid. The rutile TiO2 films, which are only a few nanometer in thickness, appear to have a high donor density and a bandgap of 3.4 eV. To explore the electron/hole (e/h) recombination mechanism, intensity-modulated photocurrent spectroscopy (IMPS) has been applied, from which insight into the nature of e/h surface recombination could be obtained. It appears that the recombination rate is not limited by capture of majority carriers, as is usually the case, but by surface diffusion of intermediate species in the photooxidation reaction.