Understanding the ferroelectric switching in freestanding BiFeO₃ films

The goal to achieve the low-voltage switching in BiFeO₃ could be significant for reducing the energy consumption for the electric field control of magnetism, and promoting the prospect of ultra-low power ferroelectric memories. Although several strategies have been proposed, such as size scaling, strain engineering or achieving high-quality of crystals, the value of switching voltage has been still limited. In this work, we design the freestanding BiFeO₃ films for elucidating the ferroelectricity without the “clamping effect” from substrate. Due to the release of the imposed strain from substrate, the lattice distortion and a reduced c/a value are observed. And the ferroelectric domain pattern of BiFeO₃ shows a highly-order to disorder transition after freestanding. This inhomogeneous domain structure might be induced by the release of the clamping effect from the substrate and could be one of the reasons for the reduced switching voltage in the freestanding BiFeO₃. It indicates that the freestanding methodology may pave a new pathway toward the next-generation low-power ferroelectric memory.