Thermal Transport and Thermoelectric Energy Conversion in Nanomaterials – Li Shi

Date: Mon. October 5th, 2009, 12:30 pm-1:30 pm
Location: Rockefeller 221

The high charge carrier mobility and thermal conductivity of carbon nanotubes and graphene have attracted interest in their applications for nanoelectronics and thermal management. On the other hand, the suppressed lattice thermal conductivity of semiconducting nanowires and thin films may give rise to enhanced figure of merit of thermoelectric materials. In an effort to better understand the potentials and challenges of these nanomaterials-enabled designs, we have developed a set of experimental methods to characterize electron and phonon transports in individual nanostructures. Our recent experiments have demonstrated the measurement of the thermal conductance together with the chirality of the same individual single- walled carbon nanotube, and shown that the thermal conductivity of graphene supported on silicon dioxide is lower than that of graphite because of scattering with substrate phonons. In addition, we have found that both surface scattering and unit cell complexi ty suppress the lattice thermal conductivity of higher manganese silicide nanowires and wurtzite phase InAs nanowires, and suggested that the charge carrier concentration and mobility in a nanowire can be obtained from thermoelectric measurement. Our measurements further reveal that interface scattering suppresses the in-plane thermal conductivity of disordered layered WSe2-containing thin films although the ultralow cross-plane thermal conductivity is caused by highly anisotropic phonon transport in the WSe2 layers instead of interface scattering.