NIRT: Nanoscale Organic Circuits and Sensors

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AbstractThis proposal was received in response to Nanoscale Science and Engineering initiative, NSF 01-157, category NIRT. It focuses on organic semiconductor based nanoscale transistors, a particularly important area of activity where much remains to be understood and discovered. Organic nanoscale transistors make use of fabrication approaches ranging from molecular self-assembly to advanced nanolithography. This, together with the considerable flexibility in designing and synthesizing a range of semiconducting materials offers hope that such devices may one day be components in a new generation of electronic circuits. The ability to confine and manipulate electric charges on the spatial scale of a molecule is an important advantage for molecular electronics. The proposed project aims at combining self-assembly and advanced nanolithography to realize two families of nanoscale transistor devices that will enable the systematic evaluation of these devices as components in electronic circuits. Crucial to the study is the use of advanced high k dielectrics in organic nano-transistors. This will lower the operating voltage of the devices as well as permit the induction of very large densities of charge, which in turn has been shown to open up new domains in charge transport with associated applications. The project will involve device characterization by conventional methods as well as by scanning probe methods. Additionally, it will involve extensive characterization of interfaces between organic semiconductors and gate insulators, and morphological characterization of self-assembled organic layers with a lateral resolution down to 1 nm. Large-area organic transistors have been shown in the recent past to have unique properties such as chemical sensing and light-emission. The chemical sensing aspects of nanotransistors will be examined in detail for the first time This study will combine chemical design of semiconductors with receptor groups to bind specific analytes with detailed characterization of the chemical nature of the interaction between semiconductor and analyte. Among other properties of nanoscale transistors that will be explored is superconductivity. Superconductivity has been observed recently in large-area polymer transistors and among the suggested applications of such transistors includes quantum information processing. Finally, a new approach to fabricate circuits is proposed in which the organic nano-transistor circuitry is compatible with Si-circuitry. This architecture permits (in principle) the sharing of functionality between the Si circuitry and the organic circuitry. The key aspect of the fabrication scheme is the use of an up-side down approach to fabricate organic circuitry, in which the interconnects are defined first followed by the gate level and finally the source-drain level. Thus the fragile molecular materials are not exposed to harsh processing environments.