Device applications of skyrmion-like polar nanodomains

Ferroelectrics are materials in which spontaneous polarization can be reversed through the application of an electric field. As storage media continues to be miniaturized, ferroelectrics utilizing topological polar domains have emerged as a solution to improve data storage. Notably, such nanodomains can be tuned, which opens up new avenues to device manipulation.

Recognizing that skyrmion-like polar nanodomains — stable topological structures characterized by knots of spinning orbits — enable high-density storage, Chen et al. aimed to overcome barriers in their device applications.

“There lacks a simple and controllable way to create and erase skyrmion-like polar nanodomains in ferroelectric and dielectric heterostructures, making device applications elusive,” said author Di Wu. “This inspired us to investigate exotic polar nanodomains in epitaxial SrTiO₃/PbTiO₃ bilayers.”

To develop tunable skyrmion-like polar nanodomains, Chen et al. varied the thickness of the SrTiO₃ capping layer in SrTiO₃/PbTiO₃ bilayer structures. This allowed for competition between elastic and electrostatic energies to be increased or decreased, resulting in the appearance of nanodomains.

By adjusting the pulse voltage and pulse width of an atomic force microscopy tip, the authors found that skyrmion-like polar nanodomains can be created or erased at prescribed sizes and positions. If the presence and absence of nanodomains can be interpreted as digital ‘0’ and ‘1’, non-destructive, high-density memory applications utilizing ferroelectrics can be developed.

In the future, the authors plan to investigate the application of tunable nanodomains in other materials.

“Exploring topological nanodomains in other bilayers is underway,” said Wu. “The mechanism of conductive domain walls also deserves further investigation.”

Source: “Highly tunable skyrmion-like polar nanodomains for high-density ferroelectric hard disks,” by Hongying Chen, Wenda Yang, Cheng Li, Peijie Jiao, Zhiyu Liu, Chuanjie Lin, Yaoyao Chen, Guo Tian, Yu Deng, Yuefeng Nie, Yongjun Wu, Jun-Ming Liu, Zijian Hong, Xingsen Gao, and Di Wu, Applied Physics Reviews (2024). The article can be accessed at https://doi.org/10.1063/5.0209179 .