Distinctive in-Plane Cleavage Behaviors of Two-Dimensional Layered Materials
Y Guo and CR Liu and QF Yin and CR Wei and SH Lin and TB Hoffman and YD Zhao and JH Edgar and Q Chen and SP Lau and JF Dai and HM Yao and HSP Wong and Y Chai, ACS NANO, 10, 8980-8988 (2016).
Mechanical exfoliation from bulk layered crystal is widely used for preparing two-dimensional (2D) layered materials, which involves not only out-of-plane interlayer cleavage but also in-plane fracture. Through a statistical analysis on the exfoliated 2D flakes, we reveal the in-plane cleavage behaviors of six representative layered materials, including graphene, h-BN, 2H phase MoS2, IT phase PtS2, FePS3, and black phosphorus. In addition to the well-known interlayer cleavage, these 2D layered materials show a distinctive tendency to fracture along certain in-plane crystallography orientations. With theoretical modeling and analysis, these distinct in-plane cleavage behaviors can be understood as a result of the competition between the release of the elastic energy and the increase of the surface energy during the fracture process. More importantly, these in-plane cleavage behaviors provide a fast and noninvasive method using optical microscopy to identify the lattice direction of mechanical exfoliated 2D layered materials.
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