Time-Resolved Mapping of Charge Carrier Dynamics and Defect-Mediated Migration Barriers in TiO2

Abstract

The spatiotemporal behavior of charge carriers in metal oxides governs their performance in photocatalytic and electronic applications, yet remains poorly understood at the nanoscale. Here, we use time-resolved atomic force microscopy (TR-AFM) to map charge transport in TiO₂ under controlled surface irradiation and thermal conditions. Our measurements reveal pronounced spatial variability in carrier migration times and activation energies, driven by local defect landscapes. Irradiation-induced surface defects are found to lower migration barriers, enhancing carrier relaxation. Notably, we observe electrostatic memory effects, with residual electric fields modulating migration dynamics across hundreds of nanometers. Temperature-dependent studies further reveal a tunable interaction between defect-mediated migration and thermal activation. These findings provide direct insight into nanoscale charge transport in TiO₂ and highlight the role of defect engineering and thermal management in optimizing oxide-based devices for energy conversion and sensing.