Cross-wire tunnel junction

In principle a STM should be adequate to measure the electrical resistance of a single molecule since it suffices to measure I-V curves of the metal (tip)-molecule-metal (substrate) system. However, published results in the literature concerning this subject have to be considered cautiously because of the generally unknown nature of the molecule-metal contacts. An illustrative experiment demonstrates the relevance of the interface (Kushmerick et al, 2002). This experimental work studies charge transport using the cross-wire tunnel junction technique, where two... 

FIGURE 3.8. (a) Schematic representation of the crossed-wire tunnel junction (not to scale), (b) Plots of I(V) (current in logarithmic scale) for junctions formed from three molecular compounds. (Reprinted with permission from Ref.50 Kushmetrick etai, J.Am. Chem. Soc. 124,10654—10655 (2002). Copyright 2002 American Chemical Society.)... 

The crossed-wire junction method was used to measure charge transport through OPE 95 and OPV 110. The order of conductance was again found to follow the series OPV > OPE > dodecanedithiol [41], despite disruption of conjugation in 110 by the two CH2 units. Oriented SAMs of molecule 112 displayed a slight rectification of the tunnel current when measured in a crossed-wire geometry [42], thus reflecting the asymmetry of the molecule. 

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