High resolution resistive thermometry for micro/nanoscale measurements.

High resolution thermometry plays an important role in several micro/nanoscale studies. Here, we present a detailed analysis of the resolution of resistance thermometry schemes that employ an electrical sensing current to monitor the temperature-dependent resistance. Specifically, we theoretically and experimentally analyze four different schemes where modulated or unmodulated temperatures in microdevices are measured using modulated or unmodulated sensing currents. Our analysis and experiments suggest that measurement of unmodulated temperatures using a modulated sensing current improves the resolution in comparison to a scenario where an unmodulated sensing current is used. However, depending on the exact measurement conditions, such improvements might be modest as the overall resolution may be limited by random low frequency environmental temperature fluctuations. More importantly, we find that high-resolution thermometry can be achieved in the measurement of modulated temperatures. Specifically, we show that by using appropriate instrumentation and a 10 kΩ platinum resistance thermometer it is possible to measure modulated temperatures (0.5-20 Hz) with a resolution of about 20-100 μK. The advances described here will enable a dramatic improvement in the heat-current resolution of resistive thermometry based microdevices that are used for probing nanoscale phonon and photon transport.