Wednesday, November 4, 2009: 10:50 AM
Charolais (Camino Real Hotel)
Thermal conductivity and electrical resistivity of nanoscale materials differ considerably from their bulk counterparts. Effects such as surface and grain boundary scattering significantly influence electrical and thermal properties of nanoscale materials with important practical implications for current and future electronics, photonics, and thermoelectrics. Conventional wisdom for metals holds that thermal transport is predominantly by electrons and transport by phonons is negligible. This assumption is used to justify the use of the Wiedemann-Franz law to infer thermal conductivity based on measurements of electrical resistivity. Recently experiments suggest a breakdown of the Wiedemann-Franz law at the nanoscale. This talk will examine the assumption that thermal transport by phonons can be neglected. The electrical resistivities and thermal conductivities of aluminum nanowires of various sizes are directly measured. These values are used in conjunction with the Boltzmann transport equation to conclude that the Wiedemann-Franz law describes the electronic component of thermal conductivity, but that the phonon term must also be considered. A novel experimental device is described for the direct thermal conductivity measurements. Support is acknowledged from the National Science Foundation and J. F Maddox Foundation.