SiC siligraphene: a novel SiC allotrope with wide tunable direct band gap and strong anisotropy

Abstract

By employing ab initio evolutionary algorithm, we predict two novel metastable structures whose energies are just higher than g-SiC but lower than other two-dimensional SiC siligraphenes reported so far. One is composed of 4-6-8 C-Si rings named tho-SiC siligraphene and the other one is composed of 5-6-8 rings named pho-SiC siligraphene. They are almost equal in energy, but interestingly, our calculations demonstrate that tho-SiC siligraphene is a semiconductor like g-SiC, while pho-SiC siligraphene is a two-dimensional metal. Besides, different from g-SiC which is very easy to switch from a direct band gap to indirect band gap semiconductor and exhibits homogenous isotropy characteristic under biaxial strains, tho-SiC siligraphene keeps consistently direct band gap from 1.02 eV to 1.98 eV as the uniaxial strain increases from -9% to 9% and it shows strong anisotropic electronic structures. The obtained calculation results indicate that tho-SiC siligraphene may be a better candidate than g-SiC in the application of light-emitting devices in the future.