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VERSION:2.0
CALSCALE:GREGORIAN
PRODID:UW-Madison-Physics-Events
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SEQUENCE:0
UID:UW-Physics-Event-2051
DTSTART:20110210T160000Z
DURATION:PT1H0M0S
DTSTAMP:20260420T135023Z
LAST-MODIFIED:20110124T221258Z
LOCATION:5310 Chamberlin
SUMMARY:Electrical and Optical Characterization of Molecular Nanojunct
 ions\, R. G. Herb Condensed Matter Seminar\, Dan Ward\, Rice Universit
 y
DESCRIPTION:Electrical conduction at the single molecule scale has bee
 n studied extensively with molecular nanojunctions. However\, our unde
 rstanding is hindered by a lack of methods for simultaneous local imag
 ing or spectroscopy to determine the conformation and local environmen
 t of the molecule of interest.  Plasmon based surface-enhanced spectro
 scopies are one method of probing the conformation and environment of 
 a molecule.  Using a combination of simultaneous electrical and optica
 l measurements we have successfully demonstrated that nanojunctions ar
 e excellent surface-enhanced Raman spectroscopy substrates that can ha
 ve single molecule sensitivity.   In this talk I will discuss two rece
 nt experimental results\, including an investigation into optically dr
 iven currents in bare nanojunctions.  The resulting photocurrent is du
 e to rectification of the enhanced optical electric field in the nanog
 ap. From low frequency electrical measurements we are able to infer th
 e magnitude of the enhanced electric field\, with inferred enhancement
 s exceeding 1000.  I will also discuss electrical and optical heating 
 in molecular nanojunctions.  Our measurements show that molecular vibr
 ations and conduction electrons in nanojunctions\, under electrical bi
 as or laser illumination\, can be driven from equilibrium to effective
  temperatures exceeding 600 K.  We observe that individual vibrations 
 are not in thermal equilibrium with one another\, the conduction elect
 rons\, or the substrate. <br>
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URL:https://www.physics.wisc.edu/events/?id=2051
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