Two-dimensional β-phase group-VA binary compounds for versatile electronic and optical properties

Abstract

Two-dimensional (2D) group-VA materials (e.g., monolayer black phosphorus) have recently gained interest due to their extremely high carrier mobility. In this paper, a family of 2D β phase binary group-VA monolayers, including PAs, PSb, PBi, AsSb, AsBi and SbBi, were explored using DFT calculations. They were confirmed to be stable free-standing materials having versatile electronic structures with either direct or indirect band gaps ranging from 0.90 to 2.39 eV, predicted at the HSE06 level with spin-orbital coupling corrections. More interestingly, a linear correlation was explored between the cohesive energy and band gaps of different composites with average ionization energies (AIEs). This provided an opportunity to engineer the desirable properties of these 2D materials from AIEs of component atoms. Furthermore, these 2D binary compounds exhibited extremely small effective masses of carriers (e.g., 0.12 m₀ of electrons for SbBi monolayer) and a high electron mobility of 589.87 cm⁻² V⁻¹ s⁻¹, predicted at the HSE06 level with spin-orbital coupling corrections. Finally, these monolayers showed considerable absorption of solar energy as well as suitable band alignments for photocatalytic water-splitting. Such results revealed a group of novel 2D materials based on group-VA compounds that are expected to be fabricated and utilized as nanoelectronics and photocatalysts.