Electron Transfer through a Monolayer of Hexadecylquinolinium Tricyanoquinodimethanide

Langmuir, 15 (11), 4011 -4017, 1999. 10.1021/la990099r S0743-7463(99)00099-2
Web Release Date: April 30, 1999

Electron Transfer through a Monolayer of Hexadecylquinolinium Tricyanoquinodimethanide

Dominique Vuillaume*

Institut d'Électronique et de Micro-électronique du Nord (IEMN), CNRS, and Department of Physics at the Institut Supérieur d'Electronique du Nord (ISEN), Avenue Poincaré, BP69, F-59652 Cedex, Villeneuve d'Ascq, France

Bo Chen and Robert M. Metzger

Laboratory for Molecular Electronics, Department of Chemistry, University of Alabama, P.O. Box 870336, Tuscaloosa, Alabama 35487-0336

Received February 1, 1999

In Final Form: March 19, 1999

Abstract:

Electron transfer through a Langmuir-Blodgett monolayer of hexadecylquinolinium tricyanoquinodimethanide (C₁₆H₃₃Q-3CNQ) sandwiched between metal electrodes is studied carefully. Either current rectification (rectification ratio as high as ~20) for positive bias applied on the metal overlayer or symmetric current voltage curves were observed for samples with the highest resistivity. More leaky devices (resistivity of about a decade lower) show rectification (with a smaller ratio 5) for a negative bias on the top electrode. These results are analyzed regarding various mechanisms: (1) Aviram and Ratner proposal for a molecular diode, (2) geometrical asymmetry of the metal/Langmuir-Blodgett monolayer/metal structure, and (3) a polarization charge density effect. This study leads us to confirm that the observed electron-transfer properties through the C₁₆H₃₃Q-3CNQ LB monolayers are not only due to possible geometrical asymmetry in the metal/LB monolayer/metal structure but are also related to the strong asymmetry of the donor-- bridge-acceptor C₁₆H₃₃Q-3CNQ molecules.

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