High-Throughput Measurement Platform for Simultaneous Thermal and Thermoelectric Property Characterization

Event Date: July 6, 2015
Authors: Collier Miers and Amy Marconnet
Journal: International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems (InterPACK) 2015
Paper URL: Conference Website
International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems (InterPACK), San Francisco, CA, 2015.

Waste heat is a prevalent energy source that can be utilized via thermoelectric devices that convert a temperature difference to electricity. Unfortunately many thermoelectric materials have insufficient performance when compared to price per Watt. This means that scalable thermoelectric materials must be developed with a low $/Watt performance metric, which can be accomplished by nanostructuring of the material. The thermoelectric figure of merit ZT =  Sσ T / k  is a measure efficiency and measures the ratio of the power factor,  Sσ, to the thermal conductivity, k. Studies have shown that nanostructuring of materials can substantially reduce the thermal conductivity, which can result in an improved ZT if the nanostructuring can target mainly the phonon transport, while having minimal impact on the electrons. Development of such materials requires accurate characterization of three separate material properties: the Seebeck Coefficient, electrical conductivity, and thermal conductivity. We have developed a measurement structure permitting simultaneous cross-plane property characterization of all three properties on a device scale thermoelectric leg. The structure has been designed to accommodate a wide range of different materials to provide a versatile platform for multi-property characterization of novel materials. The structure was optimized for combined property measurements using numerical analysis, then its performance benchmarked using known materials for verification. A 1-D solution, based upon the Feldman Algorithm for diffusive heat transfer in a general layered structure, is used for data analysis to avoid computationally expensive finite element solutions, while still achieving less than 5% error across the range of thermal conductivities of interest for thermoelectric materials. Additionally, we have designed and implemented a high-throughput measurement platform to conduct testing of up to four separate devices at a time. These tests utilize a shielded testing enclosure to preserve low-level signal integrity, temperature controlled measurement stage with a stable set point between -50oC to 200oC, and spring-loaded electrical connections to avoid the time consuming processes of wire bonding or lead-wire soldering. Standard electrical instrumentation is utilized for measurement of the Seebeck coefficient and electrical conductivity, while a frequency based electro-thermal technique known as the 3ω method is used to determine the thermal conductivity. This integrated sample design combined with our high-throughput testing apparatus facilitates rapid, high accuracy property characterization, thus decreasing the development time for new scalable thermoelectric materials.