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

Abstract

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.