Ergodic and Nonergodic Charge Carrier Dynamics at the Atomic Scale

Lattice defects determine the electronic, optoelectronic, and chemical properties of materials. Current knowledge regarding the dynamics of vacancy mobility in perovskites is solely based on volume and/or time-averaged measurements. The underlying nanoscale phenomena are thus averaged over scales orders of magnitude larger than the governing spatial and temporal lattice dimensions. This impedes our understanding of the basic physical principles governing defect migration in inorganic materials. I present the ergodic and nonergodic dynamics of vacancy migration at the relevant spatial and temporal scales using time-resolved atomic force microscopy techniques. Our findings demonstrate that the time constant associated with vacancy migration is a local property and can change drastically on the short length and time scales, such that nonergodic states lead to a dramatic increase in the migration barrier [1]. This correlated spatial and temporal variation in vacancy dynamics can extend hundreds of nanometers across the surface of perovskites. I will also demonstrate the effect of photo-induced surface oxygen vacancies on the charge carrier dynamics in metal-oxide semiconducting films [2].