NER: Carbon Nanotube Devices and Integrated Systems

University Of Southern California, Los Angeles CA

Investigators

Abstract

PROPOSAL NO.: 0102955 PRINCIPAL INVESTIGATOR: Zhou, Chongwu INSTITUTION NAME: University of Southern California TITLE: NER: Carbon Nanotube Devices and Integrated Systems This is a proposal to design, build and evaluate various novel nanotube devices and integrated systems. Specifically I propose to make n type field effect transistors (FET), nanotube p-n junctions, and an integrated single-molecule CMOS inverter. This research is exploratory in nature; however, if successful, will advance our understanding of the fundamental properties of nanotubes and produce practical nanoscale devices for the real world. There has been a great deal of research into carbon nanotubes in the past few years. P type field effect transistors have been demonstrated consisting of semiconductive nanotubes with a silicon substrate backgate separated from the tube by a layer of SiO2. Despite the utmost interest in developing n type FETs to enable nanoscale CMOS circuits, the research effort has been hampered by lack of an effective doping method for nanotubes. I propose to demonstrate a simple, effective and reliable method to electrostatically dope nanotubes into n type, thus paving the way for n type FETs, p-n junctions and integrated systems. This new method will employ TiO2 instead of SiO2 as the gate dielectric. With a dielectric constant of 30 for TiO2, as compared to 3.8 for SiO2, the gate utilizing TiO2 will be seven times more effective than previously reported, and our preliminary analysis confirms that with a reasonable gate bias (~ 10 V), a nanotube can be electrostatically doped into n type, thereby producing an n type FETs. Furthermore, carbon nanotube p-n junctions will be demonstrated with a split-gate technique, by depositing TiO2 onto a semiconductive nanotube contacted with source and drain electrodes, and patterning two gate electrodes atop the TiO2, each covering half of the tube. By controlling these two gate biases independently, one can tune the left half tube into p type and the right half into n type, thus creating a p-n junction in between, which provides an ideal system for studying the depletion and screening in one dimension. Finally, a simple integrated system will be demonstrated by attaching an electrode to the center of a semiconductive nanotube in addition to the source and drain electrodes. This center electrode divides the nanotube into two segments and serves as the output of the circuit. The silicon substrate backgate with TiO2 dielectric layer will serve as the circuit input and be used to tune one tube segment to function as an n type FET and the other segment as a p type FET, thereby forming the worlds first single molecule inverter.