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Electron transport through thin organic films in metal- insulator-metal junctions based on self-assembled monolayers

Holmlin, R. Erik and Haag, Rainer and Chabinyc, Michael L. and Ismagilov, Rustem F. and Cohen, Adam E. and Terfort, Andreas and Rampi, Maria Anita and Whitesides, George M. (2001) Electron transport through thin organic films in metal- insulator-metal junctions based on self-assembled monolayers. Journal of the American Chemical Society, 123 (21). pp. 5075-5085. ISSN 0002-7863.

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This paper describes an experimentally simple system for measuring rates of electron transport across organic thin films having a range of molecular structures. The system uses a metal−insulator−metal junction based on self-assembled monolayers (SAMs); it is particularly easy to assemble. The junction consists of a SAM supported on a silver film (Ag-SAM(1)) in contact with a second SAM supported on the surface of a drop of mercury (Hg-SAM(2))that is, a Ag-SAM(1)SAM(2)-Hg junction. SAM(1) and SAM(2) can be derived from the same or different thiols. The current that flowed across junctions with SAMs of aliphatic thiols or aromatic thiols on Ag and a SAM of hexadecane thiol on Hg depended both on the molecular structure and on the thickness of the SAM on Ag:  the current density at a bias of 0.5 V ranged from 2 × 10^-10 A/cm^2 for HS(CH_2)_15CH_3 on Ag to 1 × 10^-6 A/cm^2 for HS(CH_2)_7CH_3 on Ag, and from 3 × 10^-6 A/cm^2 for HS(Ph)_3H (Ph = 1,4-C_6H4_) on Ag to 7 × 10^-4 A/cm^2 for HSPhH on Ag. The current density increased roughly linearly with the area of contact between SAM(1) and SAM(2), and it was not different between Ag films that were 100 or 200 nm thick. The current−voltage curves were symmetrical around V = 0. The current density decreased with increasing distance between the electrodes according to the relation I = I0e-βdAg,Hg, where dAg,Hg is the distance between the electrodes, and β is the structure-dependent attenuation factor for the molecules making up SAM(1). At an applied potential of 0.5 V, β was 0.87 ± 0.1 Å-1 for alkanethiols, 0.61 ± 0.1 Å-1 for oligophenylene thiols, and 0.67 ± 0.1 Å-1 for benzylic derivatives of oligophenylene thiols. The values of β did not depend significantly on applied potential over the range of 0.1 to 1 V. These junctions provide a test bed with which to screen the intrinsic electrical properties of SAMs made up of molecules with different structures; information obtained using these junctions will be useful in correlating molecular structure and rates of electron transport.

Item Type:Article
Related URLs:
URLURL TypeDescription Information
Chabinyc, Michael L.0000-0003-4641-3508
Ismagilov, Rustem F.0000-0002-3680-4399
Whitesides, George M.0000-0001-9451-2442
Additional Information:Copyright © 2001 American Chemical Society. Published In Issue: May 30, 2001. Received November 22, 2000. This work was supported by the ONR, DARPA, and the NSF (ECS-9729405). R.E.H. and M.L.C. thank the National Institutes of Health for postdoctoral fellowships and R.H. thanks the Deutsche Forschungsgemeinschaft and the BASF-fellowship program for financial support. Supporting Information Available Experimental details of control experiments, plots of current−voltage data, and a detailed discussion of the statistical analysis of the data (PDF). This material is available free of charge via the Internet at
Errata:The affiliation listed for Dr. Andreas Terfort should have been the following:  Institute for Inorganic and Applied Chemistry, University of Hamburg, 20146, Hamburg, Germany. The compounds supplied by Dr. Terfort and used in this paper were synthesized at Hamburg. 06/21/2002
Funding AgencyGrant Number
Office of Naval Research (ONR)UNSPECIFIED
Defense Advanced Research Projects Agency (DARPA)UNSPECIFIED
Deutsche Forschungsgemeinschaft (DFG)UNSPECIFIED
Subject Keywords:molecular wires; alkanethiol monolayers; biological molecules; distance dependence; free-energy; rhodobacter-sphaeroides; charge-transport; reaction centers; pathway analysis; transfer rates
Issue or Number:21
Record Number:CaltechAUTHORS:20130821-160718693
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Official Citation:Electron Transport through Thin Organic Films in Metal−Insulator−Metal Junctions Based on Self-Assembled Monolayers R. Erik Holmlin, Rainer Haag, Michael L. Chabinyc, Rustem F. Ismagilov, Adam E. Cohen, Andreas Terfort, Maria Anita Rampi and, George M. Whitesides Journal of the American Chemical Society 2001 123 (21), 5075-5085
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:40793
Deposited By: Whitney Barlow
Deposited On:23 Aug 2013 21:13
Last Modified:09 Mar 2020 13:19

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