Nanocrack in MoS₂ manipulated by T-stress in modified boundary layer model

Abstract MoS 2 is expected to replace silicon-based field-effect transistors and continue Moore’s law. However, thin-film MoS 2 transistors on flexible substrates are prone to nanocracking under bending conditions. Although classical fracture mechanics provides a broad understandings of its crack tip field, how the higher-order T -stress term influences the nanofracture remains to be investigated. Using molecular dynamic simulations and modified boundary layer models, we show that T -stress regulates the nonlinear stress, plastic zones, and distortion around the crack tip, thereby changes fracture toughness and cracking direction. Under mode I loading, fracture toughness increases monotonically with rising T -stress. With the introduction of mode II loading ( K II ), the interplay between T -stress and K II can decrease fracture toughness as T -stress exceeds a critical value. Furthermore, negative T -stress tends to impedes crack deflection, whereas positive T -stress tends to promote it. However, owing to the local anisotropy in MoS 2 lattices, crack deflection always occurs in the discrete zigzag lattice orientations. Our study might provide new insights into the fracture of MoS 2 transistors under complex loads.