Differential Conductance Peak Exchange in Borromean Ring Single Molecule   Transistors
  While Single Molecule Transistors have been employed in laboratory research for a number of years, there remain many details related to charge transport that have yet to be delineated. We have used the technique of electromigration to create a nanometer-size gap for hosting a single molecule in the narrowest portion of a gold wire defined by electron beam lithography. A recently synthesized Borromean Ring complex was used as the active molecular element of the transistor devices. It is well established in Single Molecule Transistors that, for sweeps of source-drain voltage, a region of zero conductance commonly appears - known as a conductance gap - which is centered about V_sd = 0. We have observed differential conductance peaks on opposing sides of these conductance gaps exchange positions as a result of changing gate bias. We associate this property with a change in sign of the majority charge carriers flowing through the molecule. That is, a measured change in differential conductance occurs when current through a molecular energy level shifts between the flow of holes and the flow of electrons. 
Gavin D. Scott (1), Kelly S. Chichak (2), Andrea J. Peters (2), Stuart   J. Cantrill (2), J. Fraser Stoddart (2), and H. W. ...