Strain Effects of Vertical Separation and Horizontal Sliding in Commensurate Two-Dimensional Homojunctions
Ziwen Cheng, Junhui Sun, Bozhao Zhang, Zhibin Lu, Fei Ma, Guangan Zhang, Qunji Xue
Abstract
Strain, as an economic yet controllable approach for structural modulation, frequently plays a vital role in the preparation and performance optimization of two-dimensional nanomaterials (TNMs). Here, utilizing first-principles simulations, the analysis of energetics shows that the biaxial stretching and compressing could facilitate the vertical separation and horizontal sliding in graphene (Gr/Gr), hexagonal boron nitride (h-BN/h-BN), and molybdenum disulfide (MoS2/MoS2) bilayers. The quantification of electron redistribution between layers confirmed that the shifts of interlayer charge density (ρinter–) and its relative values (Δρinter–) are responsible for the vertical separation and horizontal sliding facilitated by biaxial strain. More effortless horizontal sliding was enabled by a smoother potential energy surface because a smaller Δρinter– can be acquired under compression, whereas more effortless vertical separation followed a more vulnerable surface energy because a lower ρinter– occurs under tensile strain. The vertical and horizontal division of strain effect provides a novel idea for further understanding its pivotal roles in strain engineering of commensurate-contact TNMs, such as mechanical exfoliation and solid lubrication.