Reveal stacking transition in 2D materials via Nanomechanical Resonator

The unique physical properties of two-dimensional (2D) van der Waals (vdW) materials are significantly governed by their stacking orders, which modulate interlayer coupling and crystal symmetry, giving rise to intriguing strongly correlated phases¹. Detecting these stacking orders, however, is challenging due to sub-nanometer variations in interlayer spacing. For example, in molybdenum ditelluride (MoTe₂), the 1T′ and Td phases are structurally commensurate, and are almost identical at monolayer limit. The structural differentiation between 1T’ and Td phases can only be seen in multilayer crystals and are primarily induced by layer-to-layer sliding^2,3.

In this study, we employ nanomechanical resonators to monitor strain changes during stacking order transitions using MoTe₂ as an example, demonstrating that these transitions are sensitively reflected in the resonator’s vibrational modes. We find that a minimal strain of 0.014%, triggered by stacking order shifts and revealed in mechanical resonance frequency shift. This work establishes a clear relationship between stacking order detection sensitivity and various internal and external factors, including higher-order vibrations, electrostatic energy, and baseline strain. Our nanomechanical approach presents a promising path toward constructing comprehensive phase diagrams for vdW materials and exploring ultralow-barrier stacking order transitions for applications in energy-efficient devices.



Reference:

1. Fox, C., Mao, Y., Zhang, X., Wang, Y. & Xiao, J. Stacking Order Engineering of Two-Dimensional Materials and Device Applications. Chem. Rev. 124, 1862–1898 (2024).

2. Deng, Y. et al. MoTe₂: Semiconductor or Semimetal? ACS Nano 15, 12465–12474 (2021).

3. Paul, S., Talukdar, S., Singh, R. S. & Saha, S. Topological Phase Transition in MoTe₂ : A Review. Phys. Status Solidi RRL – Rapid Res. Lett. 17, 2200420 (2023).