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

Based on first-principles calculations, a novel family of two-dimensional (2D) IV-V compounds, XC (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 hybridized, whereas the X (N, P, As and Sb) atom is nonplanar sp hybridized with one 2p orbital filled with lone pair electrons. NC , PC , AsC and SbC 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, PC , AsC and SbC monolayers can be transformed from indirect to direct semiconductors. The appropriate bandgaps and well-located band edge positions make XC monolayers potential materials for photocatalytic water splitting. XC family members also have high absorption coefficients (∼10  cm ) in the ultraviolet region and higher electron mobilities (∼10  cm  V  s ) than many known 2D semiconductors.