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Title: Barrier height formation in organic blends/metal interfaces: Case of tetrathiafulvalene-tetracyanoquinodimethane/Au(111)

The interface between the tetrathiafulvalene/tetracyanoquinodimethane (TTF-TCNQ) organic blend and the Au(111) metal surface is analyzed by Density Functional Theory calculations, including the effect of the charging energies on the molecule transport gaps. Given the strong donor and acceptor characters of the TTF and TCNQ molecules, respectively, there is a strong intermolecular interaction, with a relatively high charge transfer between the two organic materials, and between the organic layer and the metal surface. We find that the TCNQ LUMO peak is very close to the Fermi level; due to the interaction with the metal surface, the organic molecular levels are broadened, creating an important induced density of interface states (IDIS). We show that the interface energy level alignment is controlled by the charge transfer between TTF, TCNQ, and Au, and by the molecular dipoles created in the molecules because of their deformations when adsorbed on Au(111). A generalization of the Unified-IDIS model, to explain how the interface energy levels alignment is achieved for the case of this blended donor/acceptor organic layer, is presented by introducing matrix equations associated with the Charge Neutrality Levels of both organic materials and with their intermixed screening properties.
Authors:
 [1] ;  [2] ;  [3] ; ; ;  [4]
  1. Depto. Superficies y Recubrimientos, Instituto de Ciencia de Materiales de Madrid (CSIC), ES-28049 Madrid (Spain)
  2. (IFIMAC), Universidad Autónoma de Madrid, ES-28049 Madrid (Spain)
  3. Institute of Theoretical Chemistry, Universität Stuttgart, D-70569 Stuttgart (Germany)
  4. Depto. Física Teórica de la Materia Condensada and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, ES-28049 Madrid (Spain)
Publication Date:
OSTI Identifier:
22251296
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 139; Journal Issue: 21; Other Information: (c) 2013 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; DENSITY; DENSITY FUNCTIONAL METHOD; FERMI LEVEL; INTERACTIONS; INTERFACES; LAYERS; METALS; ORGANIC MATTER; SURFACES; TTF-TCNQ