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Title: Transport band gap opening at metal–organic interfaces

The interface formation between copper phthalocyanine (CuPc) and two representative metal substrates, i.e., Au and Co, was investigated by the combination of ultraviolet photoelectron spectroscopy and inverse photoelectron spectroscopy. The occupied and unoccupied molecular orbitals and thus the transport band gap of CuPc are highly influenced by film thickness, i.e., molecule substrate distance. Due to the image charge potential given by the metallic substrates the transport band gap of CuPc “opens” from (1.4 ± 0.3) eV for 1 nm thickness to (2.2 ± 0.3) eV, and saturates at this value above 10 nm CuPc thickness. The interface dipoles with values of 1.2 eV and 1.0 eV for Au and Co substrates, respectively, predominantly depend on the metal substrate work functions. X-ray photoelectron spectroscopy measurements using synchrotron radiation provide detailed information on the interaction between CuPc and the two metal substrates. While charge transfer from the Au or Co substrate to the Cu metal center is present only at sub-monolayer coverages, the authors observe a net charge transfer from the molecule to the Co substrate for films in the nm range. Consequently, the Fermi level is shifted as in the case of a p-type doping of the molecule. This is, however, a competing phenomenon to the energy band shiftsmore » due to the image charge potential.« less
Authors:
; ;  [1] ; ;  [2] ;  [3]
  1. Semiconductor Physics, Technische Universität Chemnitz, D-09107 Chemnitz (Germany)
  2. Solid Surfaces Analysis, Technische Universität Chemnitz, D-09107 Chemnitz (Germany)
  3. Electronic and Optical Properties Department, IFW Dresden, D-01171 Dresden (Germany)
Publication Date:
OSTI Identifier:
22318063
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Vacuum Science and Technology. A, Vacuum, Surfaces and Films; Journal Volume: 32; Journal Issue: 4; Other Information: (c) 2014 American Vacuum Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; COPPER COMPLEXES; FERMI LEVEL; METALS; ORGANOMETALLIC COMPOUNDS; PHOTOELECTRON SPECTROSCOPY; PHTHALOCYANINES; SYNCHROTRON RADIATION