High-density thermoelectric power generation and nanoscale thermal metrology

Abstract

Thermoelectric power generation has been around for over 50 years but has seen very little large scale implementation due to the inherently low efficiencies and powers available from known materials. Recent material advances appear to have improved the technology's prospects. In this work we show that significantly increased generated power densities are possible even for established material technologies provided that parasitic losses are controlled and effective strategies are found for handling the large resulting heat fluxes. We optimize the performance of a thermoelectric generator in this regime, and discuss fundamental performance limits in this context. We present a design of a thermoelectric generator using conventional material and a microchannel heat sink that we predict can generate many times the power of a conventional thermoelectric, at a comparable efficiency. A high temperature vacuum test station is used to characterize the power generation, efficiency, and material properties of thermoelectric materials and generators. The results of a series of studies on various bulk and thin-film materials are presented, as well as packaged generator performance. The method of CCD thermoreflectance imaging is pursued in this thesis as a quantitative means for making noncontact temperature measurements on solid-state samples at the micro- and nano-scale. We develop and test a theory of the instrument and the measurement process to rigorously characterize the accuracy and precision of the resulting thermal images. We experimentally demonstrate sub-micron spatial resolution and sub-20 mK temperature resolution with this tool. High-resolution thermal images of thermoelectric elements, polysilicon-gate field effect transistors, and other integrated electronic devices are presented.