| Molecular electronics offers a low cost and nanoscale alternative to create devices for electronic switching, high-density memory, and chemical/biological sensing applications. Structures fabricated in both metal-molecule-metal (MMM) and metal-molecule-semiconductor (MMS) configurations have proven to be interesting test beds to study the electronic and structural properties of molecular devices. The use of semiconductors as contacts allows us to tailor doping densities and control electrostatic properties of the devices. However, difficulties with top contact metal deposition, leading to undesirable effects in the devices, have been a source of variability in electrical characteristics. In an attempt to address these issues, this thesis studies the effect that different metal deposition techniques have on molecular devices. Observations about the amount of metal penetration through the monolayer can be made by correlating electrical data to spectroscopic data for the various techniques. In order to block metal penetration, graphene has been employed as a conductive, protective layer between the metal top contact and the molecular layer. The fabrication of a metal-graphene-molecule-semiconductor device (MGMS) addresses issues of electrical and structural problems in molecular devices. The effects from graphene integration were studied spectroscopically and electrically. The fabrication of a MGMS device lead to experiments conducted with molecules containing molecular headgroups that exhibit interesting electrical properties. The use of a graphene interlayer significantly improved the bias/time stability of the devices, allowing electronic charging or memory effects to be observed and quantified in these MGMS devices. |
