Fracture behavior of SiGe nanosheets: Mechanics of monocrystalline vs. polycrystalline structure

Abstract

2D materials present promising features, but their intrinsic defects, especially at high temperatures, should be considered for usage under harsh conditions. Molecular dynamics simulations were utilized in this work to explore the mechanics of monocrystalline and polycrystalline (PC) silicon–germanium nanosheets (MSiGeNS and PSiGeNS, respectively) as a function of temperature. The mechanical properties of MSiGeNSs decreased by increase of temperature in both armchair and zigzag directions. Likewise, Young's modulus, E and failure stress, σf of decreased by increasing grain-size and randomness, while failure strain, ∊f remained almost unaffected. Ultimately, the study of the mechanical properties of MSiGeNS subjected to different sizes of cracks and notches as a function of temperature showed that increasing crack length, notch radius, and temperature reduced all the properties of defective MSiGeNS. Samples possessing circular notches showed poorer properties compared to those with a crack defect. Moreover, the stress intensity factor of cracked MSiGeNS dropped sharply by temperature rise.