Polydimethylsiloxane (PDMS)-assisted non-destructive transient thermoreflectance characterizations

The conventional pump–probe thermoreflectance (pump–probe TR) techniques are routinely performed on a thin (typically <100 nm) metal transducer deposited on samples, ensuring the most fundamental principle of thermoreflectance: the reflectance change (∆R/R) of the sample surface is directly and linearly related to the temperature change (∆T) within a finite temperature range. However, general metal coating methods may damage the sample by forming a mixed layer with the sample. In this article, we present a non-destructive pump–probe transient thermoreflectance (TTR) characterization using the polydimethylsiloxane (PDMS)-assisted metal transfer technique. Our method utilizes PDMS dry transfer to transfer common transducer metals (Au and Al) to the target substrate. This method effectively avoids impurities and damage to the sample. In particular, we have utilized Au as a transition layer to study the application of Al transfer in TTR measurements. The substrate thermal conductivity measurement results show that they can all be used for TTR measurement, and the thermal boundary conductance results show that the transferred metals have low bonding to the substrate. In addition, Al/Au can be transferred over a large area at room temperature compared to Au. After measurement, the samples can be restored to their original state by a simple cleaning method. This method provides a simple and reliable way to characterize samples without metal coating for TTR.