Green Diamond: A Superhard Boron Carbonitride with Bandgap in Green-Light Region and Anisotropic High Carrier Mobilities

The development of new multifunctional superhard materials beyond diamond is a great challenge for materials science and industry application. A new diamond-like boron carbonitride material (BC6N) formed by covalently alternated stacking of two-dimensional BC3 and C3N monolayers is systemically investigated through first-principles method. The electronic structure calculations show that the new structure is a direct bandgap semiconductor with a bandgap of 2.404 eV (HSE06). It exhibits anisotropic high carrier mobility (μLh = 1.88 × 104 cm2 V–1 s–1), varied absorbance in visible light and different regions of UV light, and theoretical Vickers hardness of 81.34 GPa, close to that of diamond. Furthermore, it is easily synthesizable due to its exothermic nature when reacted from the interlayer fusion of the BC3 and C3N monolayers in a bottom-up synthesis strategy. In addition, the properties of 3D-BC6N-I can be tuned by applying strain, changing stacking patterns, and 2D-nanolization. The excellent mechanical, electronic, and optical properties and good synthesizability suggest that the new structure (named as “green diamond”) may find broad applications as a superhard and high-temperature material as well as a semiconductor and optical devices beyond diamond.