Conductance of nanoscale junctions consisting of a molecular monolayer in contact with different metal electrodes is studied. The characteristic energy scales of conductance are determined from the temperature dependence and from the non-linear current-voltage characteristics. Conductance measured at small bias follows Arrhenius behaviour. The effective activation energies are dependent on the metal contacts. The activation energies, typically in the range of 5-150 meV, are small compared to the expected molecular energy level spacings. The nature of the low-energy states remains unclear; however, some mechanisms, such as doping of the molecular layer by metal atoms, can be excluded. For certain metal pairs, the energies extracted from the onset of the non-linearity correspond to the low-bias activation energies, while for other metals this is not observed. These differences are probably caused by the differences in the relative topography of metal electrodes defining the effective conducting paths through the molecular layer.
ASJC Scopus subject areas
- Materials Science(all)
- Mechanics of Materials
- Mechanical Engineering
- Electrical and Electronic Engineering