title: Solvent exfoliation of electronic-grade, two-dimensional black phosphorus.
abstract: Solution dispersions of two-dimensional (2D) black phosphorus (BP)--often referred to as phosphorene--are achieved by solvent exfoliation. These pristine, electronic-grade BP dispersions are produced with anhydrous organic solvents in a sealed-tip ultrasonication system, which circumvents BP degradation that would otherwise occur via solvated O2 or H2O. Among conventional solvents, N-methylpyrrolidone (NMP) is found to provide stable, highly concentrated (∼0.4 mg/mL) BP dispersions. Atomic force microscopy, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy show that the structure and chemistry of solvent-exfoliated BP nanosheets are comparable to mechanically exfoliated BP flakes. Additionally, residual NMP from the liquid-phase processing suppresses the rate of BP oxidation in ambient conditions. Solvent-exfoliated BP nanosheet field-effect transistors exhibit ambipolar behavior with current on/off ratios and mobilities up to ∼10(4) and ∼50 cm(2) V(-1) s(-1), respectively. Overall, this study shows that stable, highly concentrated, electronic-grade 2D BP dispersions can be realized by scalable solvent exfoliation, thereby presenting opportunities for large-area, high-performance BP device applications.
authors.affiliation: †Department of Materials Science and Engineering, ‡Graduate Program in Applied Physics, §Department of Chemistry, and ∥Department of Medicine, Northwestern University, Evanston, Illinois 60208, United States.
authors.forename: Joohoon
authors.initials: J
authors.lastname: Kang
authors.affiliation: †Department of Materials Science and Engineering, ‡Graduate Program in Applied Physics, §Department of Chemistry, and ∥Department of Medicine, Northwestern University, Evanston, Illinois 60208, United States.
authors.forename: Joshua D
authors.initials: JD
authors.lastname: Wood
authors.affiliation: †Department of Materials Science and Engineering, ‡Graduate Program in Applied Physics, §Department of Chemistry, and ∥Department of Medicine, Northwestern University, Evanston, Illinois 60208, United States.
authors.forename: Spencer A
authors.initials: SA
authors.lastname: Wells
authors.affiliation: †Department of Materials Science and Engineering, ‡Graduate Program in Applied Physics, §Department of Chemistry, and ∥Department of Medicine, Northwestern University, Evanston, Illinois 60208, United States.
authors.forename: Jae-Hyeok
authors.initials: JH
authors.lastname: Lee
authors.affiliation: †Department of Materials Science and Engineering, ‡Graduate Program in Applied Physics, §Department of Chemistry, and ∥Department of Medicine, Northwestern University, Evanston, Illinois 60208, United States.
authors.forename: Xiaolong
authors.initials: X
authors.lastname: Liu
authors.affiliation: †Department of Materials Science and Engineering, ‡Graduate Program in Applied Physics, §Department of Chemistry, and ∥Department of Medicine, Northwestern University, Evanston, Illinois 60208, United States.
authors.forename: Kan-Sheng
authors.initials: KS
authors.lastname: Chen
authors.affiliation: †Department of Materials Science and Engineering, ‡Graduate Program in Applied Physics, §Department of Chemistry, and ∥Department of Medicine, Northwestern University, Evanston, Illinois 60208, United States.
authors.forename: Mark C
authors.initials: MC
authors.lastname: Hersam
keywords: anhydrous; centrifugation; degradation; field-effect transistor; liquid phase; organic solvent; phosphorene