A High‐Speed Dielectric Approach to Track Domain Structure Evolution in Operating Ferroelectric Devices

Ferroelectric switching is a fundamental process underpinning the functionality of modern electronic devices, yet the dynamic evolution of ferroelectric domain structures, especially in thin films, remains poorly understood. While established techniques such as piezoresponse force microscopy and transmission electron microscopy successfully image ferroelectric domains, they fail to capture global transient domain dynamics due to resolution limits and slow acquisition. In addition, performing in operando measurements on functional devices is highly impractical with these methods. This gap has hindered progress in understanding and controlling ferroelectric switching in thin films, which is critical for applications from nonvolatile memories to sensors. Here, we introduce a novel approach using amplitude‐modulated dielectric signals in the frequency domain to drastically reduce acquisition times to microseconds, instead of seconds. This method allows real‐time, nondestructive, and in operando tracking of domain wall density and mobility in ferroelectric devices, overcoming the limitations of existing techniques. By applying this approach to (Ba,Ca)TiO 3 thin films, we directly probe transient states in response to electric pulses, revealing previously inaccessible dynamics. This breakthrough opens new avenues for studying dynamic domain switching in thin films and promises to advance the design of ferroelectric materials for next‐generation electronic devices.