Mesoscopic microwave dispersion in ferroelectric thin films.

The microwave dielectric response of a ferroelectric thin film is measured locally using time-resolved confocal scanning optical microscopy. Measurements performed on an ensemble of nanometer-scale regions show a well-defined phase shift between the paraelectric and ferroelectric response at 2-4 GHz. Application of a static electric field produces large local variations in the phase of the ferroelectric response. These variations are attributed to the growth of in-plane ferroelectric nanodomains whose size-dependent relaxation frequencies lead to strong dielectric dispersion at mesoscopic scales.