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. Measureme nts 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 t o the growth of in-plane ferroelectric nanodomains whose size-dependent rel axation frequencies lead to strong dielectric dispersion at mesoscopic scal es.