Electronic structures of air-exposed few-layer black phosphorus by optical spectroscopy

TL;DR

This study reveals how air exposure alters the optical and electronic properties of few-layer black phosphorus, offering a new method for band-structure engineering through controlled oxidation.

Contribution

It demonstrates that air exposure causes significant optical changes in FL-BP, providing a novel approach for tuning its electronic structure via oxidation.

Findings

Air exposure broadens resonance peaks and increases Stokes shift.

Air exposure induces blue shifts in IR and PL spectra, especially in thinner samples.

Oxidation offers a new way to engineer band structure in FL-BP.

Abstract

The electronic structure of few-layer(FL) black phosphorus(BP) sensitively depends on the sample thickness, strain and doping. In this paper, we show that it is also vulnerable to air-exposure. The oxidation of BP caused by air-exposure gives several optical signatures, including the broadening of resonance peaks and increased Stokes shift between infrared (IR) absorption and photoluminescence (PL) peaks. More importantly, air exposure causes blue shifts of all resonance peaks in IR absorption and PL spectra, with more prominent effects for thinner samples and higher order subband transitions. Our study alludes a convenient and exotic way for band-structure engineering of FL-BP through controllable air-exposure or defect creation.