title: Photooxidation and quantum confinement effects in exfoliated black phosphorus.
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.
authors.affiliation: Regroupement Québécois sur les Matériaux de Pointe (RQMP) and Département de physique, Université de Montréal, Montréal, Québec H3C 3J7, Canada.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Favron
authors.affiliation: RQMP and Département de chimie, Université de Montréal, Montréal, Québec H3C 3J7, Canada.
authors.forename: Etienne
authors.initials: E
authors.lastname: Gaufrès
authors.affiliation: Laboratoire d'Etude des Microstructures, UMR 104 CNRS-Onera, Châtillon, France.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Fossard
authors.affiliation: RQMP and Département de génie physique, Polytechnique Montréal, Montréal, Québec H3C 3A7, Canada.
authors.forename: Anne-Laurence
authors.initials: AL
authors.lastname: Phaneuf-L'Heureux
authors.affiliation: RQMP and Département de chimie, Université de Montréal, Montréal, Québec H3C 3J7, Canada.
authors.forename: Nathalie Y-W
authors.initials: NY
authors.lastname: Tang
authors.affiliation: RQMP and Département de chimie, Université de Montréal, Montréal, Québec H3C 3J7, Canada.
authors.forename: Pierre L
authors.initials: PL
authors.lastname: Lévesque
authors.affiliation: Laboratoire d'Etude des Microstructures, UMR 104 CNRS-Onera, Châtillon, France.
authors.forename: Annick
authors.initials: A
authors.lastname: Loiseau
authors.affiliation: Regroupement Québécois sur les Matériaux de Pointe (RQMP) and Département de physique, Université de Montréal, Montréal, Québec H3C 3J7, Canada.
authors.forename: Richard
authors.initials: R
authors.lastname: Leonelli
authors.affiliation: RQMP and Département de génie physique, Polytechnique Montréal, Montréal, Québec H3C 3A7, Canada.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Francoeur
authors.affiliation: RQMP and Département de chimie, Université de Montréal, Montréal, Québec H3C 3J7, Canada.
authors.forename: Richard
authors.initials: R
authors.lastname: Martel