Two-Dimensional Anisotropic C10 Carbon Allotrope with Mechanically Tunable Band Gap

A high band gap, two-dimensional (2D) twisted octagonal (TO-)C 10 allotrope of carbon is proposed. This dynamically and mechanically stable structure shows thermal stability up to 500 K and shows one of the largest Young's modulus of 306.4 GPa nm (close to graphene) among 2D carbon derivatives. TO-C 10 also possesses one of the highest 2.94 eV (3.97 eV by HSE06) indirect band gap among reported 2D allotropes of carbon. Owing to structural anisotropy with respect to the basal plane and strong directional sp 3 bonding, the band gap of the structure is tuned with high strain endurance along with variation in the band gap subject to applied direction of strain. The nature of the band gap also changes between indirect and direct on account of variation in the valence band states, dominantly governed by carbon atoms in the less symmetrically bonded ladder sites. Further, the band gap can be tuned with doping of Si and Ge and also by forming one-directional nanoribbons. Owing to structural inhomogeneity and inherent high band gap, the proposed 2D TO-C 10 can be a potential candidate for future applications.