Charged Vacancy Defects in Black Phosphorus Monolayer Phosphorene

TL;DR

This study uses density-functional theory to analyze charged vacancy defects in phosphorene, revealing their structures, charge states, and impact on electronic properties relevant for optoelectronic applications.

Contribution

It provides a comprehensive theoretical analysis of vacancy defect structures, charge transition levels, and their effects on carrier properties in phosphorene.

Findings

Neutral vacancy has a 9-5 ring structure with 1.7 eV formation energy.

Vacancies become negatively charged at Fermi level 1.04 eV above valence band.

Negatively charged vacancies can passivate dopants and reduce mobility.

Abstract

The two-dimensional semiconductor phosphorene has attracted extensive research interests for potential applications in optoelectronics, spintronics, catalysis, sensors, and energy conversion. To harness phosphorene's potential requires a better understanding of how intrinsic defects control carrier concentration, character, and mobility. Using density-functional theory and a charge correction scheme to account for the appropriate boundary conditions, we conduct a comprehensive study of the effect of structure on the formation energy, electronic structure, and charge transition level of the charged vacancy point defects in phosphorene. We predict that the neutral vacancy exhibits a 9-5 ring structure with a formation energy of 1.7 eV and transitions to a negatively charged state at a Fermi level 1.04 eV above the valence band maximum. The corresponding optical charge transitions display sizeable Frank-Condon shifts with a large Stokes shift of 0.3 eV. Phosphorene vacancies should become negatively charged in n-doped phosphorene, which would passivate the dopants and reduce the charge carrier concentration and mobility.