Fabrication and characterization of nanoscale molecular electronic devices.

摘要

Current CMOS technology is rapidly approaching the physical limits of transistor scaling. These limits may be overcome by using nanometer-size organic molecules as functional units to transfer electrons in nanoscale devices. Organic molecules offer several advantages over conventional CMOS technology: smaller size, easy synthesis procedure, tailor-ability and finally, the ability to self-assemble on a metal substrate. Despite these advantages, the molecular electronic circuit remains a distant reality. The challenges remain in identifying molecules with potential device applications, understanding the electrical behaviors of these molecules and integrating the molecular devices into a usable circuit. In this dissertation, a nanowell test structure for the characterization of a metal-molecule-metal junction was fabricated. We proved the effectiveness of the nanowell test structure by testing different chain length of alkanethiol molecules and comparing the experimental results with the literature values. Switching with memory behavior that may have a potential application in memory devices was observed in our nanowell device from an oligo (phenylene ethnylene) (OPE) molecule with a nitro side group, commonly known as the nitro molecule. Various important switching parameters such as threshold voltages, yield of working devices, median current values and on-off ratios were reported in this dissertation. The nitro molecule was also tested in various environments and the switching behavior was found to be dependent on the molecular environments. The observed switching behavior was attributed to the conformation change of the nitro functional group, stabilized by the molecular interactions. A possible application of the switching behavior observed from the nitro molecules may be in a crossbar memory array. However, integrating the molecular electronic devices into a crossbar circuit is a difficult challenge to the scientific community. In this dissertation, the fabrication challenges were overcome and a 3x3 crossbar molecular electronic circuit was demonstrated.