Freestanding Ferroelectric bubble domains*

Ferroelectric bubble domains in complex oxide superlattices can be grown only on select substrates. This is a key bottleneck for their heterogeneous integration. Using the epitaxial layer transfer technique, we create freestanding superlattices. We find structural ripples appear in a freestanding state, but bubble domains remain intact. Using atomic and piezoresponse force microscopy, microwave impedance microscopy, and numerical calculations combining atomistic simulation and circuit model we study piezo and capacitive responses of the freestanding bubble domains. We anticipate these results will initiate a new thrust to explore non-trivial ferroelectric polar orders with arbitrary boundaries.