Analysis of the efficiency with which geometrically asymmetric metal-vacuum-metal junctions can be used for the rectification of infrared and optical radiations

The authors simulate the rectification properties of geometrically asymmetric metal–vacuum–metal junctions in which one of the metals is flat while the other is extended by a sharp tip. The authors analyze, in particular, the efficiency with which the energy of incident radiations, with frequencies in the infrared through the visible, is transferred to the electrons that cross the junction. This time-dependent electronic scattering problem is solved by using a transfer-matrix methodology. In order to validate this technique, the results achieved by using this quantum-mechanical scheme are compared with those provided by models that are based on extrapolations of static current–voltage data. The authors then discuss concepts that are relevant to the efficiency with which energy is converted in these junctions. The authors finally analyze how this efficiency is affected by the amplitude and the angular frequency of the potentials that are induced in these junctions, the work function of the metallic contacts and the spacing between these contacts.