Bulletin of the American Physical Society
2006 APS March Meeting
Monday–Friday, March 13–17, 2006; Baltimore, MD
Session P1: Electron Transport in Single Molecules |
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Sponsoring Units: DCMP Chair: Allan MacDonald, University of Texas at Austin Room: Baltimore Convention Center Ballroom IV |
Wednesday, March 15, 2006 11:15AM - 11:51AM |
P1.00001: Electrochemical gate-controlled conductance of single molecules Invited Speaker: The ability to measure and control current through a single molecule is a basic requirement towards the ultimate goal of building an electronic device using single molecules. This ability also provides one with a rather unique opportunity to study charge transport, a phenomenon that plays vital roles in many chemical, electrochemical and biological processes, on a single molecule basis. To reliably measure the current, one must: 1) provide a reproducible contact between the molecule and two probing electrodes; 2) find a signature to identify that the measured conductance is due to not only the sample molecules but also a \textit{single} sample molecule; 3) provide a third gate electrode to control the current. The method that we have used to create individual molecular junctions is to bring two electrodes into and out of contact with each other in the presence of sample molecules terminated proper linkers that can bind covalently to the electrodes. The individually created molecular junctions vary in the atomic scale details of the contact configurations, and statistical analysis is used to extract the conductance of the molecular junction with the most probable configuration. When several configurations occur with comparable probabilities, the method may result in multiple conductance values. In order to control the current through a molecule, we use an electrochemical gate in which the molecular junction is immersed in an electrolyte and biased with respect to a reference. We have studied three types of molecules: electrochemically inactive molecules, electroactive molecules that undergo irreversible redox reactions, and electroactive molecules that undergo reversible redox reactions. These molecular systems exhibit rather different electrochemical gating behaviors. [Preview Abstract] |
Wednesday, March 15, 2006 11:51AM - 12:27PM |
P1.00002: Electron Transport in Molecular Transistors Invited Speaker: We have fabricated molecular transistors by depositing molecules between nanometer-spaced electrodes created via electromigration. Electron transport in these devices is dominated by the single-electron tunneling effect. Several examples will be discussed including (1) excitations of intramolecule vibrations in single trimetal-molecule transistors, (2) room-temperature single-electron tunneling transistors using alkanedithiols – here the transport occurs through ultrasmall Au nanoparticles spontaneously formed during thiol assembly, and (3) Kondo resonance and co-tunneling behavior in metal-porphyrin and expanded-porphyrin molecule transistors. [Preview Abstract] |
Wednesday, March 15, 2006 12:27PM - 1:03PM |
P1.00003: Electron-vibron coupling in single molecule transistors Invited Speaker: I discuss coupling between electron transport and vibrational degrees of freedom in single-molecule and nanotube systems. The coupling gives rise several effects such as sidebands in the differential conductance, rectification due to polaron formation,and interesting interplay with the Kondo resonance. [Preview Abstract] |
Wednesday, March 15, 2006 1:03PM - 1:39PM |
P1.00004: Field Regulation of Single Molecule Conductivity by a Charged Atom Invited Speaker: A new concept for a single molecule transistor is demonstrated [1]. A single chargeable atom adjacent to a molecule shifts molecular energy levels into alignment with electrode levels, thereby gating current through the molecule. Seemingly paradoxically, the silicon substrate to which the molecule is covalently attached provides 2, not 1, effective contacts to the molecule. This is achieved because the single charged silicon atom is at a substantially different potential than the remainder of the substrate. Charge localization at one dangling bond is ensured by covalently capping all other surface atoms. Dopant level control and local Fermi level control can change the charge state of that atom. The same configuration is shown to be an effective transducer to an electrical signal of a single molecule detection event. Because the charged atom induced shifting results in conductivity changes of substantial magnitude, these effects are easily observed at room temperature. [1] Paul G. Piva1,Gino A. DiLabio, Jason L. Pitters, Janik Zikovsky, Moh'd Rezeq, Stanislav Dogel, Werner A. Hofer {\&} Robert A. Wolkow, Field regulation of single-molecule conductivity by a charged surface atom, NATURE \textbf{435}, 658-661 (2005) [Preview Abstract] |
Wednesday, March 15, 2006 1:39PM - 2:15PM |
P1.00005: Measurement of the conductance of single conjugated molecules Invited Speaker: |
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