Technique extends limits of resistance thermometers to below 10 Kelvin
Technique extends limits of resistance thermometers to below 10 Kelvin lead image
Resistance thermometers show decreasing temperature with decreasing resistance, but typically have limits of around 10 Kelvin since resistance saturates around that temperature for good metals. Qiao and Zhang developed a resistance thermometer that works below 10 Kelvin—a finding that could enable companies to more accurately measure the thermoelectric properties of chips with mesoscopic or microscopic samples.
The scientists found using the Kondo effect could help extend the working temperature of resistance thermometers. To achieve the Kondo effect, they introduced small magnetic impurities into a metal to change the resistance limits of that metal through scattering effects.
The authors evaporated iron in an electron beam evaporator without the presence of the sample. The lithographically patterned wafer was then loaded into the instrument, and gold and titanium were deposited. The pre-deposition of iron gave rise to the Kondo effect in the gold/titanium metal strips, as evidenced by low temperature resistance measurements.
Their resulting samples, which consisted of lithographically patterned metal strips, reproducibly showed an upturn in resistance with decreasing temperature.
“We demonstrated that our on-chip thermometers worked from 10 K down to about 0.25 K—the lowest temperature we calibrated so far,” author Ding Zhang said. “The temperature resolution can be as high as 0.002 K at 2 K.”
The authors hope to apply their method to different materials.
“In the paper, we measured the Seebeck and Nernst effects in a NbSe2 flake with a transition temperature below 10 K,” Zhang said. “We are currently carrying out a more systematic study on this material and will hopefully extend our study to other two-dimensional materials in this low temperature regime as well.”
Source: “Extension of on-chip thermometry of metal strips toward sub-10 K regime,” by Jiabin Qiao and Ding Zhang, Applied Physics Letters (2022). The article can be accessed at https://doi.org/10.1063/5.0086691 .
