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Probing Current-Voltage Properties of Electroactive SAM-Based Molecular Junctions

Grace Credo*, a, Drew Wassela, Stephan Kræmera, Ryan Fuierera, Andrew K. Boalb, Vincent M. Rotellob, Daniel L. Feldheima, and Christopher B. Gormana

aDepartment of Chemistry, North Carolina State University,
Raleigh, NC 27695, USA

bDepartment of Chemistry, University of Massachusetts-Amherst,
Amherst, MA 01003, USA

This is an abstract for a presentation given at the
10th Foresight Conference on Molecular Nanotechnology


A variety of metal-molecule-metal junctions have been used to elucidate single molecule properties in organic monolayers that are applicable in molecular electronics. For example, pore-based sandwich structures, mechanical break junctions, and Hg drop electrode top contacts have been used to characterize the current-voltage properties of organic monolayers. Studies have also employed scanning tunneling microscopy (STM) and conducting atomic force microscopy (cAFM) to probe the current-voltage properties of molecular junctions with more limited contact areas. In particular, reports of STM studies on redox-active molecular monolayers have described the use of electroactive moieties in molecular junctions to facilitate nonlinear current-voltage behavior. In a recent example, the nonlinear current-voltage phenomenon of negative differential resistance (NDR) was observed in an electroactive, ferrocene-terminated self-assembled monolayer (SAM). The identification of nonlinear current-voltage properties such as NDR for individual molecules expands the potential applicability of molecule-scale components from use as conductive wires to multi-state molecular switches.

Future efforts in molecule-based electronic component design will be aided by a vast library of information gathered by probing the electronic and chemical properties of individual molecules. An initial step to quickly probing a wide variety of molecules is to deposit molecular monolayers on an easy accessible surface, usually a flat metal substrate such as gold. Using a sharp tip as the other electrical contact we can examine how current varies as a function of applied voltage. Here, we show that nonlinear current-voltage properties (such as NDR) observed in electroactive self-assembled monolayers (SAMs) can be modified by controlling the composition of the molecular junction between a substrate (electrode 1, metal or semiconductor) and a probe tip (electrode 2, metal). In addition, we have used non-covalent molecular interactions (hydrogen bonding) to install and remove electroactive functionality in SAM-based mesoscale molecular assemblies. We use a combination of techniques (STM, conducting AFM, electrochemistry and spectroscopy) to characterize our molecular junctions.

Abstract in Microsoft Word® format 22,342 bytes

*Corresponding Address:
Grace Credo
Department of Chemistry, North Carolina State University
Box 8204, Dabney Hall, North Carolina State University, Raleigh, NC 27695-8204, USA
Phone: 919-515-8921 Fax: 919-515-8920


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