Negative Poisson's ratio and high-mobility transport anisotropy in SiC6 siligraphene

The diverse forms of silicon carbides lead to versatile properties, but an auxetic allotrope at zero pressure has never been reported. Here, using first-principles calculations we propose a two-dimensional (2D) auxetic silicon carbide material, namely SiC6 siligraphene. The plausibility of the SiC6 siligraphene is verified by the low formation energy, positive phonon spectrum and high mechanical stability. The unique framework of sp2 carbon and sp3 silicon atoms leads to unusual in-plane negative Poisson's ratios and electronic properties superior to both graphene and silicene. SiC6 siligraphene possesses a natural band gap of 0.73 eV and a high carrier mobility. The theoretical mobility in the order of 104 cm2 V−1 s−1 for electrons along the [10] direction is comparable to the hole mobility in black phosphorene, whereas the hole transport along the [110] direction is blocked. Both the electronic band structure and carrier mobility of the SiC6 siligraphene can be tuned by applying external strain. A possible synthetic route is also proposed. The exotic properties make SiC6 siligraphene a versatile and promising 2D material for applications in nanomechanics and nanoelectronics.