Photo-stimulated desorption of trimethyl acetic acid on cross-linked (1 × 2) TiO2(1 1 0) probed by scanning tunneling microscopy

Abstract Using in situ scanning tunneling microscopy (STM), we report site-specific photo-stimulated desorption of trimethyl acetic acid (TMAA) on cross-linked, (1 × 2) reconstructed TiO2(1 1 0). The comparison of the same area reveals that a significant fraction of the adsorbates still remains on the reduced surface even after prolonged UV irradiation in UHV. However, the photo-desorption of TMAA in troughs can be substantially enhanced with the combined exposure to O2. The enhancement of photo-desorption is attributed to co-adsorbed oxygen capturing excess electrons, which can partially screen photo-hole driven reactions of TMAA on the reduced surface. Such impeded photo-reactivity of TMAA is illustrated also with isolated strands on (1 × 1) TiO2(1 1 0), which exhibits much slower photo-desorption, compared to the rest of (1 × 1) surface. Moreover, the restoration of slow photo-reactivity with oxygen treatment suggests that surface can be tuned to control photoreaction of TMAA through reduction and re-oxidation cycles.