In the past few years, tremendous progress in the growth of carbon nanotubes (CNTs) has been made, which enabled the fabrication of various CNT devices for applications in electronics, biomedical techniques, and chemical/biological sensors. We have established a process to grow vertically aligned multi-walled CNTs (MWCNTs) using DC-biased plasma enhanced chemical vapor deposition (PECVD). These MWCNTs have been integrated, using a bottom-up approach, for (1) CNT interconnects and (2) nanoelectrode arrays for ultrasensitive DNA detection, both of which rely on MWCNT arrays embedded in SiO2 with detection, both of which rely on MWCNT arrays embedded in SiO2 with only the very end exposed at the surface of SiO2 matrix.
By depositing patterned metal contacts at the top surface, the embedded MWCNTs can serve as vertical interconnects in integrated circuits. The processing is fundamentally different from current Cu damascene techniques, which avoids problems associated with etching and filling of high aspect ratio nanoscale holes/trenches. The MWCNTs have demonstrated an extremely high current carrying capability, meeting the long-term requirements by International Semiconductor Technology Roadmap (ISTR).
The embedded MWCNT array can be used as a nanoelectrode array for developing electrochemical sensors. The temporal resolution and sensitivity can be dramatically improved. The low-density nanoelectrode array (<1x108 electrode/cm2) has demonstrated an extremely low detection limit down to ~ 1 nM for redox species in the solution. By functionalizing the MWCNT end with oligonucleotide probes, it can be used for detecting the hybridization of specific DNA targets through a mediator amplified guanine oxidation mechanism. The detection of both oligonucleotide targets and PCR amplicons has been demonstrated with a detection limit less than ~1000 molecules. Since the inherent guanine bases in the target DNA are used as signal moieties, this technique is label-free and can be used for rapid molecular analyses.
Dr. Jun Li is a physical scientist with NASA at Ames Research Center's Nanotechnology Center. His current research interests focus on the development of new methods to integrate the nanostructured materials to micro- and macro- sized devices in which the unique properties of individual nanoelements are utilized to improve the performance. The approach is to combine the lithographic/nonlithographic patterning, self-assembly, catalytic growth, semiconductor processing techniques, and chemical functionalization to build individual nanoelements such as carbon nanotubes (CNTs) and semiconducting nanowires (SNWs) into large-scale integrated devices. Currently he is working on CNT nanoelectrode arrays targeting at the development of ultrasensitive biosensors and the exploration of carbon nanotubes for integrate circuit interconnects.
Dr. Li received BS degree in chemistry from Wuhan University (P.R. China) in 1987, MS and PhD degree in chemistry from Princeton University in 1991 and 1995, respectively. From 1994 to 1997, he held a postdoctoral research associate position in Chemistry Department of Cornell University. He worked for Molecular Imaging Co. from 1997 to 1998 and the Institute of Materials Research and Engineering in Singapore from 1998 to 2000. He joined NASA Ames Research Center in 2000.
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EE 317, Purdue University, West Lafayette, IN