Ergodic and Nonergodic Dynamics of Oxygen Vacancy Migration at the Nanoscale in Inorganic Perovskites

Perovskites
are widely utilized either as a primary component or
as a substrate in which the dynamics of charged oxygen vacancy defects
play an important role. Current knowledge regarding the dynamics of
vacancy mobility in perovskites is solely based upon volume- and/or
time-averaged measurements. This impedes our understanding of the
basic physical principles governing defect migration in inorganic
materials. Here, we measure 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 oxygen vacancy migration is
a local property and can change drastically on short length and time
scales, such that nonergodic states lead to a dramatic increase in
the migration barrier. This correlated spatial and temporal variation
in oxygen vacancy dynamics can extend hundreds of nanometers across
the surface in inorganic perovskites.