Mechanical properties of SiC nanowires with polytypes

Abstract: In this report, we model the mechanical properties and fracture behavior of SiC nanowires with different polytypes using Molecular Dynamics (MD) simulations. The mechanical properties investigated are the Young’s modulus, the maximum tensile stress and the fracture strain. The three polytype tested are SiC (3C), (2H) and (4H). Tensile tests are performed on bulk and nanowire samples using three commonly know inter-atomic potentials: the Tersoff, the Vashishta and the MEAM potential. Our report finds large differences in how the potentials predict the mechanical properties and fracture behavior of the SiC structures. Using the MEAM potential, we perform tests on two similar sized nanowires with different side facets: one with {11-2} surfaces and one with {1-10} surfaces. The surface energies of the two surface types are estimated. Our studies find that the type of surfaces will affect the mechanical properties of the nanowire. The mechanical properties of the three SiC polytypes are obtained at four different temperatures. A dependence of the Young’s modulus on the hexagonality of unit cell is found, a dependence also reported for diamond polytypes. We further find that increasing temperatures will lower the values of the mechanical properties. Lastly, two nanowire heterostructures are constructed using diamond cubic Si and either SiC (3C) and SiC (2H). The potential energy of the interface is estimated and compared to the Si and SiC (3C)/(2H) sections of the heterostructure. We find that due to dislocations the energy is highest at the interface. The dislocation pattern of the interface is analyzed, and edge dislocations of the type 1/2<110> and 1/6<11-2> are found.