Structural, Electronic, and Optical Properties of Hexagonal XC6 (X=N, P, As, and Sb) Monolayers

Based on first-principles calculations, a novel family of two-dimensional (2D) IV-V compounds, XC6 (X=N, P, As and Sb), is proposed. These compounds exhibit excellent stability, as determined from the cohesive energies, phonon dispersion analysis, ab initio molecular dynamics (AIMD) simulations, and mechanical properties. In this type of structure, the carbon atom is sp(2) hybridized, whereas the X (N, P, As and Sb) atom is nonplanar sp(3) hybridized with one 2p(z) orbital filled with lone pair electrons. NC6, PC6, AsC6 and SbC6 monolayers are intrinsic indirect semiconductors with wide bandgaps of 2.02, 2.36, 2.77, and 2.85 eV (based on HSE06 calculations), respectively. After applying mechanical strain, PC6, AsC6 and SbC6 monolayers can be transformed from indirect to direct semiconductors. The appropriate bandgaps and well-located band edge positions make XC6 monolayers potential materials for photocatalytic water splitting. XC6 family members also have high absorption coefficients (similar to 10(5) cm(-1)) in the ultraviolet region and higher electron mobilities (similar to 10(3) cm(2) V-1 s(-1)) than many known 2D semiconductors.