| AVS 64th International Symposium & Exhibition | |
| Novel Trends in Synchrotron and FEL-Based Analysis Focus Topic | Tuesday Sessions |
| Session SA+MI-TuM |
| Session: | Overcoming the Temporal and Spatial Limits of X-Ray Scattering Methods for In-Situ Analysis |
| Presenter: | Geoff Thornton, Universty College London, UK |
| Authors: | G. Thornton, Universty College London, UK Y. Zhang, University College London, UK D. Payne, University College London, UK C. Pang, University College London, UK C. Cacho, STFC Rutherford Appleton Laboratory, UK R. Chapman, STFC Rutherford Appleton Laboratory, UK E. Springate, STFC Rutherford Appleton Laboratory, UK |
| Correspondent: | Click to Email |
Exciton recombination pathways are of paramount importance in photocatalysis because they determine the lifetime of the chemically active electrons and holes, and hence the catalytic efficiency. These pathways are not known in detail even for a prototypical material such as TiO2, where the related process of electron trapping is important in a broader range of applications (eg resistive switching). Here we use time-resolved femtosecond pump-probe photoemission spectroscopy (TRPES) to investigate exciton recombination and electron trapping in a state resolved fashion. This employed an XUV probe following an infra-red or UV pump. When an infra-red pump is employed, electrons in polaronic band gap states (BGS) are excited to the bottom of the conduction band. The subsequent recapture time of 50±10 fs is determined by directly monitoring the intensity change of the BGS and hot electrons in TRPES spectra. When a UV pump is employed, electrons are excited either from the BGS to a resonance in the CB, or from the top of the valence band (VB) to the bottom of the CB. The same trapping of hot electrons is observed as for infra-red excitation. In addition, a long lifetime component (>1 ps) of the hot electron decay and the BGS recovery are observed, pointing to trap assisted exciton recombination.