Direct Observation of Dipole Formation Triggered by Interlayer Sliding at Atomic Level in Semimetal MoTe2

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.