Edge effects on the electronic properties of phosphorene nanoribbons

TL;DR

This study uses first principles calculations to explore how edge chemistry and quantum confinement influence the electronic properties of phosphorene nanoribbons, revealing edge-dependent semiconducting or metallic behavior.

Contribution

It provides a detailed analysis of how different edge functionalizations affect the electronic properties of phosphorene nanoribbons, highlighting the role of edge states in tuning band gaps.

Findings

Armchair PNRs are semiconductors regardless of edge groups.

Zigzag PNRs can be metallic or semiconducting depending on edge chemistry.

Edge states in certain configurations reduce or close the band gap.

Abstract

Two dimensional few-layer black phosphorus crystal structures have recently fabricated and demonstrated great potential in applications of electronics. In this work, we employed first principles density functional theory calculations to study the edge effects and quantum confinement on the electronic properties of the phosphorene nanoribbons (PNR). Different edge functionalization groups, such as H, F, Cl, OH, O, S, and Se in addition to a pristine case, were studied for a series width of the ribbon up to 3.5 nm. It was found that the armchair-PNRs (APNRs) are semiconductors for all edge groups considered in this work. However, the zigzag-PNRs (ZPNRs) show either semiconductor or metallic behavior in dependence on their edge chemical groups. Family I edges (H, F, Cl, OH) form saturated bonds with P atoms and the edge states keep far away from the band gap. However, Family II edges (pristine, O, S, Se) form weak unsaturated bonds with the pz orbital of P atoms and bring edge states within the band gap. These edge states of Family II ribbons present around the Fermi level within the band gap, which close up the band gap of the ZPNRs. For the APNRs, these edge states are at the bottom of the conduction band and result in a reduced band gap.