Barrier height formation in organic blends/metal interfaces: case of tetrathiafulvalene-tetracyanoquinodimethane/Au



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Martínez, José I. and Abad, Enrique and Beltrán Finez, Juan Ignacio and Flores, Fernando (2013) Barrier height formation in organic blends/metal interfaces: case of tetrathiafulvalene-tetracyanoquinodimethane/Au. Journal of chemical physics, 139 (21). ISSN 0021-9606

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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.

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© 2013 AIP Publishing LLC. Present work was supported by Spanish MICIIN under Contract No. FIS2010-16046, the CAM under Contract No. S2009/MAT-1467, and the European Project MINOTOR (Grant No. FP7-NMP-228424). J.I.M. acknowledges funding from Spanish MICIIN and CSIC through Juan de la Cierva and JaeDoc Programs.

Uncontrolled Keywords:Energy-level alignment; Density-functional-theory; Electronic-sctructure; Charging energy; crystals; approximation; Dipole; Metal; TCNQ; TTF.
Subjects:Sciences > Physics > Electricity
Sciences > Physics > Electronics
ID Code:31354
Deposited On:27 Jul 2015 07:48
Last Modified:10 Dec 2018 14:58

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