Dynamics of photo-excited carriers in anatase TiO2 thin film investigated by pump-probe method

Abstract

We measured transient absorption spectra with pump-probe technique to investigate the dynamics of photo-excited carriers at 300 K and 12 K in anatase TiO2 epitaxial film. Although the photoluminescence (PL) originated from self-trapped excitons (STEs) vanished at 300 K, we observed the change in probe signal. On the other hand, the intensity of the transient absorption signal at 12 K was much weaker than that at 300K. Therefore the carriers at 300 K become trapped at the surface, leading to a pump-probe signal, while at 12 K, the remained carriers inside the bulk arise from STE recombination. These results suggest that the pump-probe signal is derived from the trap state(s) near the surface. © 2009 IOP Publishing Ltd.