Highly heterogeneous epitaxy of flexoelectric BaTiO3-δ membrane on Ge
Liyan Dai, Jinyan Zhao, Jingrui Li, Bohan Chen, Shijie Zhai, Zhongying Xue, Zengfeng Di, Boyuan Feng, Yanxiao Sun, Yunyun Luo, Ming Ma, Jie Zhang, Sunan Ding, Libo Zhao, Zhuangde Jiang, Wenbo Luo, Yi Quan, Jutta Schwarzkopf, Thomas Schroeder, Zuo‐Guang Ye, Ya‐Hong Xie, Wei Ren, Gang Niu
Abstract
Abstract The integration of complex oxides with a wide spectrum of functionalities on Si, Ge and flexible substrates is highly demanded for functional devices in information technology. We demonstrate the remote epitaxy of BaTiO 3 (BTO) on Ge using a graphene intermediate layer, which forms a prototype of highly heterogeneous epitaxial systems. The Ge surface orientation dictates the outcome of remote epitaxy. Single crystalline epitaxial BTO 3-δ films were grown on graphene/Ge (011), whereas graphene/Ge (001) led to textured films. The graphene plays an important role in surface passivation. The remote epitaxial deposition of BTO 3-δ follows the Volmer-Weber growth mode, with the strain being partially relaxed at the very beginning of the growth. Such BTO 3-δ films can be easily exfoliated and transferred to arbitrary substrates like Si and flexible polyimide. The transferred BTO 3-δ films possess enhanced flexoelectric properties with a gauge factor of as high as 1127. These results not only expand the understanding of heteroepitaxy, but also open a pathway for the applications of devices based on complex oxides.