(558f) Templated Fabrication and Characterization of Thermoelectric Nanowire Arrays - Toward Power-Dense and Efficient Devices

Efficient and power-dense thermoelectric devices would offer significant advantages over other forms of thermal energy conversion and control technologies. A promising route toward enhanced efficiency is through nanostructuring thermoelectric materials, the benefits of which have been predicted and demonstrated by many. However, cost effective assembly that preserves the performance enhancement of the individual nanostructures remains the dominant engineering challenge. Specifically, much attention has been focused on high aspect ratio structures such as nanowires, as they can directionally transport charge carriers and disrupt heat transport without the presence of grain boundaries or excessive interfacial sites. We are developing fabrication and characterization methods for the templated growth and assembly of thermoelectric nanostructures, including advanced low-energy nanofabrication techniques designed to both increase nanostructure anisotropy and enhance aerial power density compared to traditional templated approaches. Empirical and theoretical aspects of the fabrication methods will be highlighted with a focus on maintaining high power density (assembly density) and high efficiency (structure properties & confinement). We will discuss a self-assembly coating procedure which increases radial confinement in nanoporous oxide templates to produce densely arrayed and ultra-low diameter thermoelectric nanowires. Furthermore, we will discuss a method to supplant the loss in aerial power density introduced by the oxide template and its enhancement with respect to overall performance. Thermoelectric property measurement of thin films and anisotropic structures is non-trivial as thermal and electrical contact resistances significantly contribute to the measurement. We will briefly introduce an apparatus that measures thermopower as well as thermal and electrical conductivity designed specifically for thin film or anisotropic structures.