Fast and Slow Timescale Effects of Photoinduced Surface Oxygen Vacancies on the Charge Carrier Dynamics of TiO₂

The migration of charge carriers (<i>e.g.</i>, electrons, holes) in metal oxides, such as TiO₂, plays a vital role in (photo)catalytic applications.&lt;!--[endif]----&gt;^1-4 Nevertheless, photoinduced surface oxygen vacancies (PI-SOV) scan significantly alter the dynamics of charge carriers.&lt;!--[endif]----&gt;^1-6 Here, we study the effect of PI-SOVs (prompted by high-energy ultraviolet irradiation) on fast (<i>i.e.</i>, electrons) and slow (<i>i.e.</i>, holes) charge carriers via time-resolved atomic force microscopy (TR-AFM) measurements, while simultaneously exploring the effect of gold nanoparticles (Au-NPs). We conducted our measurements on Au-NP-deposited titanium dioxide, <i>i.e.</i>, TiO₂. Our measurements illustrate that the induced oxygen vacancy (V_O) defects result in a decrease in time constants associated with the migration of electrons. In addition, we quantified the effect of induced defects on the migration barrier of slow charge carriers, <i>i.e.</i>, holes. Our respective measurements show that PI-SOVs lower the migration barrier of holes for both the TiO₂ and TiO₂/Au-NP interface. We believe that the observed statistical difference is caused by the effect of defects over the recombination and trapping mechanisms of fast and slow charge carriers. Our results express the important effect of V_O on charge migration dynamics, which underlines the need for further studies of defects under realistic conditions.&lt;!--![endif]----&gt;&lt;!--![endif]----&gt;<br/>&lt;!--[endif]----&gt;&lt;!--[endif]----&gt; <br/>¹ <b> Bugrahan Guner</b> and Omur E. Dagdeviren, ACS Applied Electronic Materials <b>4</b> (8), 4085 (2022).<br/>² <b>Bugrahan Guner</b>, Simon Laflamme, and Omur E. Dagdeviren, Review of Scientific Instruments <b>94</b> (6) (2023).<br/>³ Orcun Dincer, <b>Bugrahan Guner</b>, and Omur E. Dagdeviren, APL Materials <b>12</b> (2) (2024).<br/>⁴ <b>Bugrahan Guner</b>, Orcun Dincer, and Omur E. Dagdeviren, ACS Applied Energy Materials <b>7</b> (6), 2292 (2024).<br/>⁵ Omur E. Dagdeviren, Daniel Glass, Riccardo Sapienza, Emiliano Cortés, Stefan A. Maier, Ivan P. Parkin, Peter Grütter, and Raul Quesada-Cabrera, Nano Letters (2021).<br/>⁶ Omur E. Dagdeviren, Aaron Mascaro, Shuaishuai Yuan, Javad Shirani, Kirk H. Bevan, and Peter Grütter, Nano Letters <b>20</b> (10), 7530 (2020).<br/> <br/>Funding information:<br/>This work was supported by the Canada Economic Development Fund, Natural Sciences and Engineering Research Council of Canada, and Le Fonds de Recherche du Québec - Nature et Technologies.<br/>&lt;!--![endif]----&gt;&lt;!--![endif]----&gt;