First author: Chao Xu
Corresponding Author: Ye Zhu
Communications unit: The Hong Kong Polytechnic University
Two-dimensional (2D) materials exhibit excellent mechanical properties, enabling them to be used as flexible and stretchable ultra-thin devices. As the origin of several extraordinary mechanical behaviors, iron elasticity has also been theoretically predicted in two-dimensional materials, but has so far lacked experimental validation and research. Recently, the Ye Zhu Research Group of the Hong Kong Polytechnic University published a research paper entitled "Two-dimensional ferroelasticity in van der Waals β'-In2Se3" in the internationally renowned journal Nature Communications. They demonstrated experimental proofs of two-dimensional iron elasticity in β' and chemical vapor deposition, down to several layer thicknesses. They used atomic resolution electron microscopy and in situ X-ray diffraction to quantitatively identify two-dimensional spontaneous strains resulting from in-plane antiferroelectric distortion. Symmetry isometric change of direction produces three domain variants separated by 60° and 120° domain walls (DW). The mechanical conversion between these ferroelastic domains was achieved under an external strain of ≤0.5%, demonstrating the feasibility of customizing the anti-iron electrode structure and DW mode through mechanical stimulation. The detailed domain switching mechanisms through DW propagation and domain nucleation are unlocked, and the effects of 3D stacking on this 2D iron elasticity are also discussed. The 2D iron elasticity observed here should be widely used in 2D materials with anisotropic lattice distortion, including 1T' transition metal disulfides with Peierls distortion and 2D ferroelectrics such as the SnTe family, giving the attractive potential to adjust 2D functionality through strain or DW engineering.
Figure 1: Antiferroelectric coupling spontaneous strain in β'-In2Se3
Figure 2: Multi-domain and DW structures in β'-In2Se3
Figure 3: Angle-resolved polarized light imaging of multi-domain patterns in β'-In2Se3
Figure 4: Iron elastic conversion in stripped β'-In2Se3 sheets
Figure 5: Two-dimensional iron elasticity of ultra-thin β'-In2Se3 sheets grown in CVD
Figure 6: Surface wrinkles on 120° DW due to 3D stacking in 3R β'-In2Se3
Figure 7: Sloping 60° DW due to 3R β'-In2Se3 resulting from 3D stacking
Original link:
https://www.nature.com/articles/s41467-021-23882-7
Homepage of the main corresponding author of the paper:
https://www.polyu.edu.hk/en/ap/people/academic-staff/dr-ye-zhu/