2021 Virtual Undergraduate Research Symposium
2021 Virtual Undergraduate Research Symposium
Experimental Platform for Cryogenic Thermal Conductivity Measurements
Experimental Platform for Cryogenic Thermal Conductivity Measurements
2ND PLACE POSTER
PROJECT NUMBER: 83 | AUTHOR: Portia Allen, Physics
MENTOR: Meenakshi Singh, Physics
ABSTRACT
Thermal conductivity measurement techniques are well-established at room temperature but become more challenging at cryogenic temperatures. The development of a dedicated thin film measurement platform for sub-Kelvin temperatures allows for the measurement of thermal conductivity of a range of materials at cryogenic temperatures. Here, we have developed and characterized an experimental platform for the measurement of thermal conductivity below 1 K. The use of suspended Si-N platforms ensures thermal isolation of the sample. Local joule heaters provide a controllable temperature gradient across the platforms. Carbon-platinum (C-Pt) composite, fabricated using focused ion beam (FIB) assisted deposition, acts as a highly sensitive, local, resistive thermometer. While suspended platforms have previously been used for thermal conductivity measurements, the integration of highly sensitive, locally deposited cryogenic thermometers allows for more precise measurements over a wider temperature range, making this platform ideal for cryogenic measurements.
PRESENTATION
AUTHOR BIOGRAPHY
Portia is a current sophomore, majoring in Engineering Physics and minoring in Data Science. She is the lab manager for the departmental shared physics lab, and this is her third year doing research for Dr. Singh’s Quantum Materials and Devices research group. Portia has presented her research at a couple (virtual) conferences over the past two years and has co-authored a publication for the international journal Carbon. Her research in low-temperature thermoelectric effects has provided a solid foundation for her interest in quantum engineering, and she plans to pursue a graduate degree in quantum engineering in the future.
Good progress! Do you make the Si3N4 bridges or are they commercially available?
Thank you! The bridges I’m using were provided to us directly by Dr. Zink from Denver University, and fabricated as outlined here: https://aip.scitation.org/doi/10.1063/1.3078025
Great work Portia! What was the thought behind using Si-N platforms (what qualities do they possess that make them work well in these systems, etc.)? Was there any thought of ever using any other material for testing?
Thanks! The Si-N bridges are fairly standard for use at low temperatures, since they have low thermal conductivity and are electrically insulating, which makes them good for low noise measurements. Since we were given the bridges by DU for testing, there wasn’t really much choice in materials.
Cool project Portia!(Pun fully intended) How fragile are the thermometers?
Haha thanks Paul. The thermometers are fairly fragile, due to their size. Even small static shocks are enough to completely vaporize them (trust me on this one).
Great work, Portia! What specific applications do you see these devices potentially being used in and how scalable is their production?
Thank you! These devices are good for low temperature thermal conductivity measurements, and could potentially be used for other low temperature characterizations as well. This is applicable in many cutting-edge fields like quantum thermodynamics, as well as for the development and fabrication of micro and nanoscale electronic devices. Scalable production might be difficult though, just due to the delicacy of the fabrication process.