Two-dimensional carbon allotropes with tunable direct band gaps and high carrier mobility

Using first-principles calculations, two sp(2) + sp(3)-hybridized two-dimensional (2D) carbon allotropes with stable orthorhombic structures are predicted in this work. Both structures are composed of tetra-, penta-, and hexarings of carbon atoms, known as TPH-I carbon and TPH-II carbon. We demonstrate that they can be obtained from penta-graphene by the Stone-Wales (SW) transformation. TPH-I carbon has an inherent direct band gap of 2.704 eV, while TPH-II carbon has a quasi-direct band gap of 2.361 eV. After applying uniaxial strain, TPH-I and TPH-II carbon will have tunable direct band gaps in the range of 2.441-2.812 eV and 2.468-2.7562 eV, respectively. Their electrons and holes mobilities are found to be anisotropic. TPH-I carbon shows extraordinary room temperature in-plane electron mobility of similar to 7.9 x 10(4) cm(2) V (-1) s(-1) and TPH-II carbon shows high hole mobility of -1.5 x 10(4) cm(2) V-1 s(-1). Both novel carbon sheets exhibit strong absorption of visible light. And their intrinsic anisotropic optical properties allow optical determination of the crystalline orientation. In addition, TPH-I carbon is a potential photocatalyst for the water splitting reaction.

Automated summary

Using first-principles calculations, two stable orthorhombic sp(2) + sp(3)-hybridized two-dimensional carbon allotropes were predicted, with tunable electronic properties through uniaxial strain and potential applications in optics and photocatalysis.