In-plane thermal conductivity measurement on nanoscale conductive materials with on-substrate device configuration

In this study, we measure the in-plane thermal conductivity of palladium (Pd) nanowire with varying length (3–50 µm) and width (100–250 nm). The bridges are fabricated by electron beam lithography with an on-substrate measurement configuration. The measurements are performed on substrates with 190 nm and 2.9 µm thick thermal oxide using a 4-probe steady-state DC Joule heating method, and several suspended structure are also prepared to investigate the accuracy of the on-substrate results. For the on-substrate measurements, the thermal conductivity is estimated for short nanowires assuming the magnitude of the heat loss to the substrate from measurements of longer nanowires. As a result, the measured thermal conductivity is 30 ± 5 W/mK for suspended short nanowires at room temperature, and the estimated thermal conductivity for the on-substrate samples are consistent with this value. The measurements on the substrate with 2.9 µm oxide result in small variations between samples (± 5 W/mK), while the results on 190 nm thick oxide has a larger variation and uncertainty (> ± 20 W/mK) due to the uncertainty in the magnitude of the heat loss to the substrate. Sufficient measurement accuracy is only achieved if the heat loss to the substrate can be estimated or measured with high accuracy.