Assembling molecular electronic junctions one molecule at a time

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Journal titleNano Letters
Pages47254729; # of pages: 5
Subjectnanomaterial; article; chemistry; crystallization; electronics; equipment; equipment design; instrumentation; materials testing; methodology; microelectrode; nanotechnology; particle size; ultrastructure; Crystallization; Electronics; Equipment Design; Equipment Failure Analysis; Materials Testing; Microelectrodes; Miniaturization; Nanostructures; Nanotechnology; Particle Size; Alkane monolayers; Azobenzene molecules; Conducting surfaces; Contact areas; Current voltage curve; Decay constants; Exponential dependence; Intermolecular interactions; Metal atoms; Metal deposition; Metal diffusion; Metal vapor; Molecular conductance; Molecular electronic junction; Molecular junction; Molecular layer; Molecular length; Molecular monolayer; Quantitative comparison; Single molecule conductance; Single-molecule devices; Structural disturbances; Gold; Gold coatings; Metals; Molecular electronics; Monolayers; Paraffins; Vapors; Molecules
AbstractDiffusion of metal atoms onto a molecular monolayer attached to a conducting surface permits electronic contact to the molecules with minimal heat transfer or structural disturbance. Surface-mediated metal deposition (SDMD) involves contact between "cold" diffusing metal atoms and molecules, due to shielding of the molecules from direct exposure to metal vapor. Measurement of the current through the molecular layer during metal diffusion permits observation of molecular conductance for junctions containing as few as one molecule. Discrete conductance steps were observed for 1-10 molecules within a monolayer during a single deposition run, corresponding to "recruitment" of additional molecules as the contact area between the diffusing Au layer and molecules increases. For alkane monolayers, the molecular conductance measured with SDMD exhibited an exponential dependence on molecular length with a decay constant (β) of 0.90 per CH 2 group, comparable to that observed by other techniques. Molecular conductance values were determined for three azobenzene molecules, and correlated with the offset between the molecular HOMO and the contact Fermi level, as expected for hole-mediated tunneling. Current-voltage curves were obtained during metal deposition showed no change in shape for junctions containing 1, 2, and 10 molecules, implying minimal intermolecular interactions as single molecule devices transitioned into several molecules devices. SDMD represents a "soft" metal deposition method capable of providing single molecule conductance values, then providing quantitative comparisons to molecular junctions containing 10 6 to 10 10 molecules. © 2011 American Chemical Society.
Publication date
AffiliationNational Research Council Canada (NRC-CNRC); National Institute for Nanotechnology (NINT-INNT)
Peer reviewedYes
NPARC number21271044
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Record identifier008df114-0993-4069-8f08-0a47bc0282c3
Record created2014-03-24
Record modified2016-05-09
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