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Atomically resolved band bending effects in a p-n heterojunction of Cu$_2$O and a cobalt macrocycle


Leuenberger, Dominik; Zabka, Wolf-D; Shah, Oliver-F R; Schnidrig, Stephan; Probst, Benjamin; Alberto, Roger; Osterwalder, Jürg (2017). Atomically resolved band bending effects in a p-n heterojunction of Cu$_2$O and a cobalt macrocycle. Nano letters, 17(11):6620-6625.

Abstract

We present a hetero junction based on macrocyclic hydrogen evolution catalysts (HEC) physisorbed on a single crystalline Cu$_2$O(111) surface. Angle-resolved X-ray photoelectron spectroscopy (ARXPS) provides the spatial resolution of the band bending within the first nanometer of the subsurface region. Oxygen vacancies on the Cu$_2$O(111) surface cause a downward band bending which is conserved upon adsorption of HEC layers of various thicknesses. This allows photoexcited electrons to be directed toward the surface where they can be made available for the reduction of protons by the HEC. Furthermore, Poisson’s equation relates more subtle changes in the measured ARXPS spectra to the local charge density profile within the first 7 Å away from the surface and with atomic resolution. All observations are consistent with a polarization of the molecular layer in response to the electrical field at the oxide surface, which should be a general phenomenon at such organic-oxide heterointerfaces.

Abstract

We present a hetero junction based on macrocyclic hydrogen evolution catalysts (HEC) physisorbed on a single crystalline Cu$_2$O(111) surface. Angle-resolved X-ray photoelectron spectroscopy (ARXPS) provides the spatial resolution of the band bending within the first nanometer of the subsurface region. Oxygen vacancies on the Cu$_2$O(111) surface cause a downward band bending which is conserved upon adsorption of HEC layers of various thicknesses. This allows photoexcited electrons to be directed toward the surface where they can be made available for the reduction of protons by the HEC. Furthermore, Poisson’s equation relates more subtle changes in the measured ARXPS spectra to the local charge density profile within the first 7 Å away from the surface and with atomic resolution. All observations are consistent with a polarization of the molecular layer in response to the electrical field at the oxide surface, which should be a general phenomenon at such organic-oxide heterointerfaces.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Chemistry
07 Faculty of Science > Physics Institute
08 University Research Priority Programs > Solar Light to Chemical Energy Conversion
Dewey Decimal Classification:530 Physics
Language:English
Date:2017
Deposited On:29 Jan 2018 12:57
Last Modified:19 Feb 2018 10:40
Publisher:American Chemical Society (ACS)
ISSN:1530-6984
OA Status:Closed
Publisher DOI:https://doi.org/10.1021/acs.nanolett.7b02486

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