Stochastic Variation in Conductance on the Nanometer Scale:  A General Phenomenon

The relative conductance of two different electroactive thiol molecules (containing ferrocene and viologen headgroups) inserted into an n -alkanethiolate background SAM was tracked over time using a scanning tunneling microscope. Both types of inserted molecules exhibited stochastic variation in their conductance. This phenomenon of “blinking” thus appears to be quite general, despite the fact that these two molecules are structurally different from one another and from molecules in which this phenomenon had been studied previously. This behavior is most simply rationalized as conformational and/or orientational changes of one or a small collection of molecules over time.