Two-Dimensional Dirac Fermions Protected by Space-Time Inversion Symmetry in Black Phosphorus

We report the realization of novel symmetry-protected Dirac fermions in a surface-doped two-dimensional (2D) semiconductor, black phosphorus. The widely tunable band gap of black phosphorus by the surface Stark effect is employed to achieve a surprisingly large band inversion up to ~0.6 eV. High-resolution angle-resolved photoemission spectra directly reveal the pair creation of Dirac points and their moving along the axis of the glide-mirror symmetry. Unlike graphene, the Dirac point of black phosphorus is stable, as protected by spacetime inversion symmetry, even in the presence of spin-orbit coupling. Our results establish black phosphorus in the inverted regime as a simple model system of 2D symmetry-protected (topological) Dirac semimetals, offering an unprecedented opportunity for the discovery of 2D Weyl semimetals

Free-patterned design of fabric-based wearable organic light-emitting diodes

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Double-shot inkjet printing for high-conductivity polymer electrode

This paper presents a printing method to form a high-conductivity patterned poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) film. A modified PEDOT: PSS ink containing a secondary dopant (dimethyl sulfoxide) and fluorosurfactant (Zonyl FS-300) was inkjet-printed to form a uniform conducting layer, and the dimethyl sulfoxide, conductivity enhancer, was over-printed onto it to further enhance its conductivity. We achieved high-conductivity greater than 1000 S cm(-1) by only using inkjet-printing technique. The mechanism of conductivity enhancement was investigated with X-ray photoelectron spectroscopy and atomic force microscopy analyses. The printing process for high-conductivity PEDOT: PSS was applied to pattern a transparent anode for the fabrication of an organic light emitting diode. (C) 2016 Elsevier B.V. All rights reserved

Double-shot inkjet printing for high-conductivity polymer electrode

This paper presents a printing method to form a high-conductivity patterned poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) film. A modified PEDOT: PSS ink containing a secondary dopant (dimethyl sulfoxide) and fluorosurfactant (Zonyl FS-300) was inkjet-printed to form a uniform conducting layer, and the dimethyl sulfoxide, conductivity enhancer, was over-printed onto it to further enhance its conductivity. We achieved high-conductivity greater than 1000 S cm(-1) by only using inkjet-printing technique. The mechanism of conductivity enhancement was investigated with X-ray photoelectron spectroscopy and atomic force microscopy analyses. The printing process for high-conductivity PEDOT: PSS was applied to pattern a transparent anode for the fabrication of an organic light emitting diode. (C) 2016 Elsevier B.V. All rights reserved.1121Nsciescopu

Electronic band structure of surface-doped black phosphorus

We present an overview on the electronic band structure of surface-doped black phosphorus. Angle resolved photoemission spectroscopy data show that the in situ deposition of potassium atoms on the surface of single-crystalline black phosphorus modulates the band gap in the wide range of 0.0-0.6 eV. At zero band gap, the surface layers of black phosphorus become a Dirac semimetal whose band dispersion is highly anisotropic, linear in armchair and quadratic in zigzag directions. In light of theoretical band calculations, we elucidate the mechanism of these band modifications as the giant Stark effect due to strong vertical electric fields induced by potassium atoms. (C) 2016 Elsevier B.V. All rights reserved.11sciescopu