Zhang Run-Sen, Jiang Jin-Wu
Shanghai Key Laboratory of Mechanics in Energy Engineering, Shanghai Institute of Applied Mathematics and Mechanics, School of Mechanics and Engineering Science, Shanghai University, Shanghai 200072, People's Republic of China.
Nanotechnology. 2021 Sep 6;32(48). doi: 10.1088/1361-6528/ac1f55.
Van der Waals heterostructures inherit many novel electronic and optical properties from their constituent atomic layers. Mechanical stability is key for realizing high-performance nanodevices based on van der Waals heterostructures. However, buckling instability is a critical mechanical issue for heterostructures associated with its two-dimensional nature. Using molecular dynamics simulations of graphene/MoSheterostructures, we demonstrate the relationship between buckling instability and the misfit strain that arises inevitably in such heterostructures. The impact of misfit strain on buckling depends on its magnitude: (1) A negative misfit strain causes a pre-compression of the graphene layer, which in turn initiates and accelerates buckling in this layer and reduces the buckling stability in the heterostructure as a whole. (2) A small positive misfit strain enhances the buckling stability of the graphene/MoSheterostructure by pre-stretching and hence decelerating the buckling of the graphene layer (where heterostructure buckling is initiated). (3) In the case of a large positive misfit strain, the graphene layer is pre-stretched while the MoSlayer is significantly pre-compressed, so that heterostructure buckling is initiated by the MoSlayer. Consequently, the buckling stability of the graphene/MoSheterostructure is reduced by increasing the large positive misfit strain. These findings are valuable for understanding the mechanical properties of van der Waals heterostructures.
范德华异质结构从其组成原子层继承了许多新颖的电学和光学性质。机械稳定性是实现基于范德华异质结构的高性能纳米器件的关键。然而，屈曲不稳定性是与其二维性质相关的异质结构的一个关键力学问题。通过对石墨烯/MoS异质结构进行分子动力学模拟，我们证明了屈曲不稳定性与这种异质结构中不可避免出现的失配应变之间的关系。失配应变对屈曲的影响取决于其大小：(1) 负失配应变会导致石墨烯层预压缩，进而引发并加速该层的屈曲，并降低整个异质结构的屈曲稳定性。(2) 小的正失配应变通过预拉伸从而减缓石墨烯层（异质结构屈曲起始处）的屈曲，增强了石墨烯/MoS异质结构的屈曲稳定性。(3) 在大的正失配应变情况下，石墨烯层被预拉伸，而Mo层被显著预压缩，使得异质结构屈曲由Mo层引发。因此，通过增加大的正失配应变，石墨烯/MoS异质结构的屈曲稳定性降低。这些发现对于理解范德华异质结构的力学性质具有重要价值。
