Abstract:

Characterizing and optimizing charge carriers (e.g., electrons, holes, ions, vacancies, etc.) is critical for advancing renewable energy applications, particularly for metal oxide (MO) systems. These investigations demand techniques capable of capturing phenomena at the correct physical scale/dimensions (i.e., submicrosecond time resolution and nanometer scale distance resolution). Custom-designed atomic force microscopy (AFM) setups and measurement techniques enable quantitative mapping of key electronic properties, including contact potential differences and charge carrier dynamics,
that can be utilized to enhance the operational lifetime of MO-based devices.

In this seminar, advanced multidimensional scanning probe microscopy (SPM) methods, including time-resolved atomic force microscopy (tr-AFM) and its unique/customized variants, are discussed for their abilities to probe/disclose the migration tendencies and dynamic behaviors of charge carriers in MO systems. Particular attention is given to metal oxides such as TiO₂, where charge carrier migration characteristics are closely tied to photocatalytic performance and are influenced by defect engineering and surface modifications. These multidimensional measurements examine sample properties as a function of temperature, location, and time. Ultraviolet (UV) irradiation is used to induce photoinduced surface oxygen vacancies to the sample systems, which can substantially alter/affect charge carrier dynamics and transport behaviors. The impact of external stimuli (e.g., UV irradiation, voltage pulses), surface agents (e.g., methanol), and introduced interfaces (e.g., Au–TiO₂) on carrier mobility, relaxation times, activation energies, and migration dynamics will be under the spotlight. The outcomes and insights obtained contribute to a deeper understanding of charge carrier dynamics for supporting the development of future MO-based systems and applications.