Thermoreflectance techniques and Raman thermometry for thermal property characterization of nanostructures

The widespread use of nanostructures and nanomaterials has opened up a whole new realm of challenges in thermal management, but also leads to possibilities for energy conversion, storage, and generation, in addition to numerous other technological applications. At the microscale and below, standard thermal measurement techniques reach their limits, and several novel methods have been developed to overcome these limitations. Among the most recent, contactless photothermal methods have been widely used and have proved their advantages in terms of versatility, temporal and spatial resolution, and even sensitivity in some situations. Among them, thermoreflectance and Raman thermometry have been used to measure the thermal properties from bulk materials to thin films, multilayers, suspended structures, and nanomaterials. This Tutorial presents the principles of these two techniques and some of their most common implementations. It expands to more advanced systems for spatial mapping and for probing of non-Fourier thermal transport. Finally, this paper concludes with discussing the limitations and perspectives of these techniques and future directions in nanoscale thermometry. I. INTRODUCTION
ICN2 is supported by the Severo Ochoa program from the Spanish Research Agency (AEI, Grant No. SEV-2017-0706) and by the CERCA Programme/Generalitat de Catalunya. ICN2 authors acknowledge support from the Spanish MICINN Project SIP (No. PGC2018-101743-B-I00) and the H2020 European FET Open project PHENOMEN (No. GA 713450). E.C.-A. acknowledges financial support from EU Project NANOPOLY (No. GA 289061). The NTNU authors are supported by the Research Council of Norway through the FRINATEK Project No. 251068 with the title: “Engineering Metal-Polymer Interface for Enhanced Heat Transfer.”