Phase diagram and superlattice structures of monolayer phosphorus carbide (P$_x$C$_{1-x}$)

TL;DR

This study investigates the phase stability and properties of monolayer phosphorus carbide (P$_x$C$_{1-x}$), revealing stable superlattice structures with promising electronic and optical characteristics for applications.

Contribution

The paper introduces a bottom-up design approach to identify stable superlattice structures of monolayer P$_x$C$_{1-x}$ with specific electronic and optical properties.

Findings

Monolayer P$_x$C$_{1-x}$ is a phase separating system.

Stable superlattice structures are composed of alternating carbon and phosphorus nanoribbons.

Predicted structures are semiconductors with band gaps from 0.2 to 1.2 eV.

Abstract

Phase stability and properties of two-dimensional phosphorus carbide, P$_x$C$_{1-x}$, are investigated using the first-principles method in combination with cluster expansion and Monte Carlo simulation. Monolayer P$_x$C$_{1-x}$ is found to be a phase separating system which indicates difficulty in fabricating monolayer P$_x$C$_{1-x}$ or crystalline P$_x$C$_{1-x}$ thin films. Nevertheless, a bottom-up design approach is used to determine the stable structures of P$_x$C$_{1-x}$ of various compositions which turn out to be superlattices consisting of alternating carbon and phosphorus 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 ranging from 0.2 to 1.2 eV. In addition, the monolayer P$_x$C$_{1-x}$ are predicted to have high carrier mobility, and high optical absorption in the ultraviolet region which shows a red-shift as the P:C ratio increases. These properties make 2D P$_x$C$_{1-x}$ promising materials for applications in electronics and optoelectronics.