title: Measuring relative barrier heights in molecular electronic junctions with transition voltage spectroscopy.
abstract: Though molecular devices exhibiting potentially useful electrical behavior have been demonstrated, a deep understanding of the factors that influence charge transport in molecular electronic junctions has yet to be fully realized. Recent work has shown that a mechanistic transition occurs from direct tunneling to field emission in molecular electronic devices. The magnitude of the voltage required to enact this transition is molecule-specific, and thus measurement of the transition voltage constitutes a form of spectroscopy. Here we determine that the transition voltage for a series of alkanethiol molecules is invariant with molecular length, while the transition voltage of a conjugated molecule depends directly on the manner in which the conjugation pathway has been extended. Finally, by examining the transition voltage as a function of contact metal, we show that this technique can be used to determine the dominant charge carrier for a given molecular junction.
authors.affiliation: National Institute of Standards and Technology, Gaithersburg, Maryland, 20899, USA.
authors.forename: Jeremy M
authors.initials: JM
authors.lastname: Beebe
authors.forename: BongSoo
authors.initials: B
authors.lastname: Kim
authors.forename: C Daniel
authors.initials: CD
authors.lastname: Frisbie
authors.forename: James G
authors.initials: JG
authors.lastname: Kushmerick
mesh_terms: D003198:Computer Simulation; D004553:Electric Conductivity; D004563:Electrochemistry / Q000379:methods*; D008422:Materials Testing / Q000379:methods*; D008956:Models, Chemical; D049329:Nanostructures / Q000737:chemistry*; D036103:Nanotechnology / Q000379:methods*; D010316:Particle Size; D012666:Semiconductors; D013057:Spectrum Analysis / Q000379:methods*