Intrinsic defects, fluctuations of the local shape, and the photo-oxidation of black phosphorus

TL;DR

This study reveals how intrinsic defects in black phosphorus facilitate photo-oxidation under visible and UV light, providing insights into its degradation process and early-stage shape and electronic property changes.

Contribution

It demonstrates that intrinsic defects lower the chemisorption barrier, enabling photo-induced oxidation in black phosphorus, which was previously thought to be inactive under visible light.

Findings

Intrinsic defects act as photo-oxidation sites.

Photo-oxidation occurs under visible and UV light.

Early shape and electronic changes are characterized.

Abstract

Black phosphorus is a monoatomic semiconducting layered material that degrades exothermically in the presence of light and ambient contaminants. Its degradation dynamics remain largely unknown. Even before degradation, local-probe studies indicate non-negligible local curvature --through a non-constant height distribution-- due to the unavoidable presence of intrinsic defects. We establish that these intrinsic defects are photo-oxidation sites because they lower the chemisorption barrier of ideal black phosphorus (> 10 eV and out of visible-range light excitations) right into the visible and ultra-violet range (1.6 to 6.8 eV), thus enabling photo-induced oxidation and dissociation of oxygen dimers. A full characterization of the material's shape and of its electronic properties at the early stages of the oxidation process is presented as well. This study thus provides fundamental insights into the degradation dynamics of this novel layered material.