Investigation on the mechanical properties and fracture phenomenon of silicon doped graphene by molecular dynamics simulation

Abstract

Silicon doping is an effective way to modulate the bandgap of graphene that might open the door for graphene to the semiconductor industries. However, the mechanical properties of silicon doped graphene (SiG) also plays an important role to realize its full potential application in the electronics industry. Electronic and optical properties of silicon doped graphene are well studied, but, our understanding of mechanical and fracture properties of the doped structure is still in its infancy. In this study, molecular dynamics (MD) simulations are conducted to investigate the tensile properties of SiG by varying the concentration of silicon. It is found that as the concentration of silicon increases, both fracture stress and strain of graphene reduces substantially. Our MD results also suggest that only 5% of silicon doping can reduce the Young's modulus of graphene by ∼15.5% along the armchair direction and ∼13.5% along the zigzag direction. Tensile properties of silicon doped graphene have been compared with boron and nitrogen doped graphene. The effect of temperature, defects and crack length on the stress–strain behavior of SiG has also been investigated. Temperature studies reveal that SiG is less sensitive to temperature compared to free stranding graphene, additionally, increasing temperature causes deterioration of both fracture stress and strain of SiG. Both defects and cracks reduce the fracture stress and fracture strain of SiG remarkably, but the sensitivity to defects and cracks for SiG is larger compared to graphene. Fracture toughness of pre-cracked SiG has been investigated and results from MD simulations are compared with Griffith's theory. It has been found that for nano-cracks, SiG with larger crack length deviates more from Griffith's criterion and the degree of deviation is larger compared to graphene. Fracture phenomenon of pre-cracked SiG and the effect of strain rate on the tensile properties of SiG have been reported as well. These results will aid the design of SiG based semiconducting nanodevices.