Scanning Tunneling Microscopy Visualization of Polaron Charge Trapping by Hydroxyls on TiO2(110)

Chi-Ming Yim; Michael Allan; Chi Lun Pang; Geoff Thornton

doi:10.1021/acs.jpcc.4c03751

Scanning Tunneling Microscopy Visualization of Polaron Charge Trapping by Hydroxyls on TiO₂(110)

J Phys Chem C Nanomater Interfaces. 2024 Aug 8;128(33):14100-14106. doi: 10.1021/acs.jpcc.4c03751. eCollection 2024 Aug 22.

Authors

Chi-Ming Yim^{1

2}, Michael Allan¹, Chi Lun Pang¹, Geoff Thornton¹

Affiliations

¹ Department of Chemistry and London Centre for Nanotechnology, University College London, 20 Gordon Street, London WC1H 0AJ, U.K.
² Tsung Dao Lee Institute and School of Physics and Astronomy, Shanghai Jiao Tong University, 1 Lisuo Road, Shanghai 201210, China.

Abstract

Using scanning tunneling microscopy (STM), we investigate the spatial distribution of the bridging hydroxyl (OH_b) bound excess electrons on the rutile TiO₂(110) surface and its temperature dependence. By performing simultaneously recorded empty and filled state imaging on single OH_bs at different temperatures in STM, we determine that the spatial distribution of the OH_b bound excess electrons retains a symmetric four-lobe structure around the OH_b at both 78 and 7 K. This indicates that OH_bs are much weaker charge traps compared to bridging O vacancies (O_b-vac). In addition, by sequentially removing the capping H of each OH_b using voltage pulses, we find that the annihilation of each OH_b is accompanied by the disappearance of some lobes in the filled state STM, thus verifying the direct correlation between OH_bs and their excess electrons.