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Nat Mater. 2015 Aug;14(8):826-32. doi: 10.1038/nmat4299. Epub 2015 May 25.

Photooxidation and quantum confinement effects in exfoliated black phosphorus.

Author information

1
Regroupement Québécois sur les Matériaux de Pointe (RQMP) and Département de physique, Université de Montréal, Montréal, Québec H3C 3J7, Canada.
2
RQMP and Département de chimie, Université de Montréal, Montréal, Québec H3C 3J7, Canada.
3
Laboratoire d'Etude des Microstructures, UMR 104 CNRS-Onera, Châtillon, France.
4
RQMP and Département de génie physique, Polytechnique Montréal, Montréal, Québec H3C 3A7, Canada.

Abstract

Thin layers of black phosphorus have recently raised interest owing to their two-dimensional (2D) semiconducting properties, such as tunable direct bandgap and high carrier mobilities. This lamellar crystal of phosphorus atoms can be exfoliated down to monolayer 2D-phosphane (also called phosphorene) using procedures similar to those used for graphene. Probing the properties has, however, been challenged by a fast degradation of the thinnest layers on exposure to ambient conditions. Herein, we investigate this chemistry using in situ Raman and transmission electron spectroscopies. The results highlight a thickness-dependent photoassisted oxidation reaction with oxygen dissolved in adsorbed water. The oxidation kinetics is consistent with a phenomenological model involving electron transfer and quantum confinement as key parameters. A procedure carried out in a glove box is used to prepare mono-, bi- and multilayer 2D-phosphane in their pristine states for further studies on the effect of layer thickness on the Raman modes. Controlled experiments in ambient conditions are shown to lower the A(g)(1)/A(g)(2) intensity ratio for ultrathin layers, a signature of oxidation.

PMID:
26006004
DOI:
10.1038/nmat4299

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