Measuring relative barrier heights in molecular electronic junctions with transition voltage spectroscopy.
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.
Beebe
Jeremy M
JM
National Institute of Standards and Technology, Gaithersburg, Maryland, 20899, USA.
Kim
BongSoo
B
Frisbie
C Daniel
CD
Kushmerick
James G
JG
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*