Prevalence of Coulomb blockade in electro-migrated junctions with conjugated and non-conjugated molecules

Conduction of electro-migration gap junctions coated with various organic molecules is studied to expose the prevalence of different transport processes. Comparisons are made between molecules with conjugated vs. non-conjugated backbones, mono- vs. dithiolated molecules, and molecules with and without large side chains. Coulomb blockade (CB) is observed in all junctions, including bare junctions and those with non-conjugated molecules, but at significantly lower prevalence than for conjugated molecules. Importantly, CB with high charging energy is seen almost exclusively on junctions with conjugated molecules.