Quasi-Planar tetracoordiante carbon Networks with tunable electronic properties combined with Ultra-High carrier mobility and optical absorption Coefficient: Two-dimensional Be2C

Tunable electronic structure, high carrier mobility and high optical absorption coefficient are three key properties for the application of two-dimensional (2D) semiconductors in nanoelectronic and optoelectronic devices. Based on first-principles calculations, we have designed a novel 2D quasi-planar material, Be2C monolayer, which contains tetracoordiante carbon structure formed by the metal bonding between carbon and four surrounding beryllium atoms. The monolayer Be2C has a wide indirect band gap of 2.33 eV (calculated by HSE06 functional), which can be regulated into a direct band gap by applying strain and changing the number of Be2C layers, leading to a change of the band gap from 0 to 2.62 eV. In addition, the monolayer Be2C has ultra-high electron mobility of 1.44 × 104 cm2V-1s−1 and light absorption coefficient of 1.12 × 106 cm−1, which are comparable to graphene and perovskite materials in solar cell. These excellent properties provide a very bright prospect for the monolayer Be2C in the applications of microelectronic and optoelectronic devices.