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4. Thermal Transport at Nanoscale Point and Line Constrictions and Interfaces

    Graduate Student Researchers: Nathan P. Malcolm, Arden L. Moore, Jae Hun Seol

    Collaboration: Prof. John R. Howell, Dr. Ravi S. Prasher (Intel)

    Sponsor: National Science Foundation

    Project Status: Current

    Thermal transport at nanometer scale point and line constrictions and interfaces is a fundamental problem that is important for a number of technologies, such as scanning probe microscopy, novel thermal interface materials, and nanostructural electronic and thermoelectric devices. As of today, few measurement results of thermal resistances at nanoscale constrictions and interfaces are available. Moreover, although there have been extensive theoretical studies of contact thermal resistance between two solids, most of the existing analytical models have been developed for macro to micro scale contacts. The research objective of this program is to measure and model thermal transport at nanoscale point and line constrictions and interfaces. Ultrahigh vacuum atomic force microscopy and nanofabricated structures will be employed to measure the thermal resistance of nanometer size point contacts, line interfaces, and Si constrictions. A molecular dynamics (MD) simulation method will be used to calculate the thermal resistance and temperature distribution at these nanoscale constrictions and interfaces. In addition to heat conduction, the calculation will investigate the influences of near- and far- field radiation transfer on the temperature distribution and thermal resistance. The results from the measurements and calculations will be correlated and used to verify and improve analytic models. The close collaboration with Dr. Prasher at Intel will have mutual benefits for the education of the participating students and the transfer of knowledge gained from this study for industrial applications.

3. Structure-Optical-Thermal Relationships of Carbon Nanotubes

    Graduate Student Researchers: Michael T. Pettes, Guangping Zhang

    Collaboration: Prof. Steve Cronin (USC)

    Sponsor: Department of Energy Office of Basic Energy Science

    Project Status: Current

    The exceptional properties of carbon nanotubes have stimulated a great deal of interest in their potential applications in computing, energy, and health care technologies. The goal of this research is to perform a set of optical, electronic, and thermal measurements on the same individual carbon nanotube characterized by transmission electron microscopy (TEM) to provide new information about several important physical phenomena that are currently not well understood. These phenomena are strongly pronounced in nanotubes due to their tight confinement of electrons and phonons, high crystal quality and true one-dimensional nature. The precise correlation of advanced optical, electronic, and thermal measurements will enable new studies and applications of carbon nanotubes.

2. Thermal Transport and Thermoelectric Measurements of Nanotransistors, Nanowires, and Superlattices

    Graduate Student Researchers: Michael T. Pettes, Jae Hun Seol

    Sponsor: National Science Foundation

    Project Status: Completed 

    As integrated circuit devices are continuously miniaturized with a minimum feature size approaching 100 nm and below, the power density increases rapidly when the same output voltage is maintained. Consequently, increased self-heating leads to a substantial elevation of the local device temperature and deteriorates the device output characteristics. This research program has two specific aims for addressing the self heating problem. The first one is to develop scanning probe microscopy methods for nanoscale mapping of temperature and voltage distributions in operating nanotransistors so as to better understand charge and heat transport phenomena in these devices. The second one is to characterize thermal transport and thermoelectric properties of nanowire and thin film superlattice materials that can potentially be used to fabricate energy-efficient thermoelectric refrigerators for on-chip spot cooling of electronic devices.

1. Nanowire Composites for On-Chip Cooling of Microelectronics

    Graduate Student Researcher: Arden L. Moore

    Sponsor: DARPA Advanced Processing and Prototyping  Center (AP2C)

    Project Status: Completed