Orientation-specific transgranular fracture behavior of CVD-grown monolayer MoS2 single crystal

Abstract

In recent times, there has been a rapidly growing interest in fracture behavior of two-dimensional materials since it is crucial for device performances. Here, we report an orientation-specific transgranular fracture behavior of a CVD-grown monolayer MoS2 single crystal investigated by various means. The underlying mechanism proposed that micro-cracks nucleated at sulfur vacancies propagate along the energy-favored zigzag directions upon fast quenching induced thermal strain, which results in an orientation-specific fracture behavior. The corresponding photoluminescence characteristic peaks undergo a blue-shift by ∼165 meV, suggesting compressive strain resided, in sharp contrast to tensile strain in a normal CVD-grown MoS2 single crystal. In addition, the combined photoemission electron microscopy and kelvin force microscopy results show the obvious surface potential variation between fractured MoS2 microflakes in some regions, ascribed to inhomogeneous interactions between MoS2 and the underlying substrate. The results reported here deepen the understanding of the fracture behavior of monolayer single crystalline MoS2, which is also adoptable in other transition metal dichalcogenide materials.