Two-dimensional molecular self-assembly approaches to nanoelectronics

The use of two-dimensional molecular self-assembly approaches to fabricate nanoelectronics devices and their circuitries were evaluated. In particular, we examined the feasibility of using DNA-based nanofabrication as an alternative manufacturing method to conventional top-down lithography and the possibility of using molecules as tailorable electronic elements in future integrated circuits.; We demonstrated the potential for exploiting the programmability of DNA templates to lay out a complex array of prototype nanocomponents with nanometer scale precision by exploiting the sequence-specific interactions and selectivity of DNA. This technique was used to assemble one or two different types of DNA-coated gold nanoparticles into regular arrays on a common structure by self-assembling to a 2D DNA scaffolding. We expanded the capability of a DNA template as a starting material to grow a 2D array of metallic nanowires with controllable inter-wire spacing. Electrical characterizations through nanowires contacted by narrow, e-beam patterned electrodes show single-electron tunneling phenomena at room temperature due to granular structures of the nanowires. In additional to the fact that the electronic properties of these templated nanowires could have applications to single electronic devices, the passive and low-leakage electrical properties of the DNA template further suggest the compatibility of the electrical and chemical environment of the DNA template for nanoelectric fabrication processes.; We explored the potential of using self-assembled monolayers (SAMs) composed organic molecules as electronic components. We conducted a basic study of electrical transport in alkanethiol SAMs with well-known tunneling characteristics and establish a reliable and effective method to electrically probe the molecules of interest using bilayer molecular junction which utilizes the Hg drop contact. The currents and breakdown voltages were found to exhibit a bias asymmetry due to the dissimilar contact electrodes. The overall electrical transport of alkanethiol junctions over a wide range of molecular chain-lengths and bias ranges were observed to be well-behaved and consistent with electronic tunneling. We also investigated and modeled the novel and inadequately understood negative differential resistance (NDR) phenomena associated with 4-[[2-amino-5-nitro-4-(phenylethynyl)phenyl]ethynyl] benzenethiol or OPE molecule. We systematically probed the time-dependence of the electrical behavior of bilayer molecular junctions fabricated from OPE and alkanethiol SAMs. The study led to the conclusion that the NDR is caused by slow charge capture during the current-voltage sweep and the resultant effects on electron tunneling through the junction, which has important implications for the understanding and possible use of such molecular junctions.