R&D: Direct Observation of Dipole Formation Triggered by Interlayer Sliding at Atomic Level in Semimetal MoTe2

Nano Letters has published an article written by Lin Liao, State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, China, and Nanostructure Research Center, Wuhan University of Technology, Wuhan 430070, China, Xianli Su, State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, China, Hao Luo, State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, China, and Nanostructure Research Center, Wuhan University of Technology, Wuhan 430070, China, Xili Wen, State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, China, , Yin Dai, School of Physics, Huazhong University of Science and Technology, Wuhan 430074, China, Keke Liu, Haoran Ge, Qingjie Zhang, State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, China, Menghao Wu, School of Physics, Huazhong University of Science and Technology, Wuhan 430074, China, Xinfeng Tang, State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, China, Jinsong Wu, State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, China, and Nanostructure Research Center, Wuhan University of Technology, Wuhan 430070, China.

Abstract: “Octahedral MoTe₂ is a nonpolar 1T′ phase and transforms into polar T_d phase at ∼260 K, along with the change of the layer stacking order. However, as it is difficult to capture the interlayer sliding at atomic resolution, the polarization formation mechanism of MoTe₂ by cooling to low temperature remains largely unclear. Here, we address the challenge by in situ cryo-(S)TEM to trace the interlayer sliding at the atomic level and the induced polarization in vdW-layered MoTe₂. When it is in the range of 300–193 K, we observed the step-by-step formation of the local T_d domain within the 1T′-I domain. Moreover, we present an atomic-scale observation of the disordered mixed stacking of 1T′/T_d phases at 110 K. Two possible sliding models are built with the sliding energy barriers (2.7 and 5.3 meV/u.c.), indicating thermally accessible sliding behavior. Our investigation of sliding-induced polarization provides meaningful insights for developing sliding ferroelectric-based nonvolatile memory devices.“