Ferroelectric Domain Branching in KDP

We observed periodic and fractal domain structures on inclined sides of thick KDP c plates by using SEM. It is found that the domains of lower ordinal pre-fractal domain structures run through the thickness, but the domains generating higher ordinal ones stick on and branch those of the lower ordinal ones near the c surfaces. The period 2L of the domain structure shows the thickness d dependence, 2L proportional to d(0.7) . These verify the ferroelectric domain branching due to a depolarization field in KDP.