Molecular Conductance - Molecular Film Experiments

Molecular film experiments generally consist of the sandwiching of a thin layer of molecules between two electrodes which are used to measure the conductance through the layer. Two of the most successful implementations of this concept have been the bulk electrode approach and in the use of nanoelectrodes. In the bulk electrode approach, a molecular film is typically immobilized onto one electrode and an upper electrode is brought into contact with it allowing for a measure of current flow as a function of applied bias voltage. The nanoelectrode class of experiments, in creatively utilizing equipment such as atomic force microscope tips and small-radius wires, are able to perform the same sorts of current versus applied bias measurements but on a much smaller number of molecules as compared to bulk electrode. For instance, the tip of an atomic force microscope can be used as a top electrode and, given the nano-scale radius of curvature of the tip, the number of molecules measured is drastically cut. The difficulties encountered in these experiments have come mainly in dealing with such thin layers of molecules which often results in problems with short-circuiting the electrodes.