Versatile electronic properties and exotic edge states of single-layer tetragonal silicon carbides

Three single-layer tetragonal silicon carbides (SiCs), termed as T1, T2 and T3, are proposed by density functional theory (DFT) computations. Although the three structures have the same topological geometry, they show versatile electronic properties from a semiconductor (T1), a semimetal (T2) to a metal (T3). The versatile properties originate from the rich bonds between Si and C atoms. The nanoribbons of the three SiCs also show interesting electronic properties. Especially, T1 nanoribbons possess exotic edge states, where electrons only distribute on one edge's silicon or carbon atoms. The band gaps of the T1 nanoribbons are constant because of no interaction between the edge states.