Thermal conductivity measurements of high and low thermal conductivity films using a scanning hot probe method in the 3ω mode and novel calibration strategies†
This work discusses measurement of thermal conductivity (k) of films using a scanning hot probe method in the 3ω mode and investigates the calibration of thermal contact parameters, specifically the thermal contact resistance (RthC) and thermal exchange radius (b) using reference samples with different thermal conductivities. RthC and b were found to have constant values (with b = 2.8 ± 0.3 μm and Rthc = 44 927 ± 7820 K W−1) for samples with thermal conductivity values ranging from 0.36 W K−1 m−1 to 1.1 W K−1 m−1. An independent strategy for the calibration of contact parameters was developed and validated for samples in this range of thermal conductivity, using a reference sample with a previously measured Seebeck coefficient and thermal conductivity. The results were found to agree with the calibration performed using multiple samples of known thermal conductivity between 0.36 and 1.1 W K−1 m−1. However, for samples in the range between 16.2 W K−1 m−1 and 53.7 W K−1 m−1, calibration experiments showed the contact parameters to have considerably different values: Rthc = 40 191 ± 1532 K W−1 and b = 428 ± 24 nm. Finally, this work demonstrates that using these calibration procedures, measurements of both highly conductive and thermally insulating films on substrates can be performed, as the measured values obtained were within 1–20% (for low k) and 5–31% (for high k) of independent measurements and/or literature reports. Thermal conductivity results are presented for a SiGe film on a glass substrate, Te film on a glass substrate, polymer films (doped with Fe nano-particles and undoped) on a glass substrate, and Au film on a Si substrate.