Phase stability and properties of two-dimensional phosphorus carbide, ${\mathrm{P}}_x{\mathrm{C}}_{1-x}$ ($0\le x\le 1$), are investigated using the first-principles method in combination with cluster expansion and Monte Carlo simulation. Monolayer ${\mathrm{P}}_x{\mathrm{C}}_{1-x}$ is found to be a phase-separating system which indicates difficulty in fabricating monolayer ${\mathrm{P}}_x{\mathrm{C}}_{1-x}$ or crystalline ${\mathrm{P}}_x{\mathrm{C}}_{1-x}$ thin films. Nevertheless, a bottom-up design approach is used to determine the stable structures of ${\mathrm{P}}_x{\mathrm{C}}_{1-x}$ of various compositions which turn out to be superlattices consisting of alternating carbon and black phosphorene nanoribbons along the armchair direction. Results of first-principles calculations indicate that once these structures are produced, they are mechanically and thermodynamically stable. All the ordered structures are predicted to be semiconductors, with band gap (Perdew-Burke-Ernzerhof) ranging from 0.2 to 1.2 eV. In addition, the monolayer ${\mathrm{P}}_x{\mathrm{C}}_{1-x}$ are predicted to have high carrier mobility, and high optical absorption in the ultraviolet region which shows a redshift as the P:C ratio increases. These properties make two-dimensional ${\mathrm{P}}_x{\mathrm{C}}_{1-x}$ promising materials for applications in electronics and optoelectronics.

• Received 11 October 2020
• Accepted 4 February 2021

DOI:https://doi.org/10.1103/PhysRevMaterials.5.024005