Raman-based Nanoscale Thermal Transport Characterization: A Critical Review

•Critically review the mechanisms of Raman spectrum response to temperatures and the conjugation of various physical and optical factors•Cover the steady-state Raman spectroscopy for temperature and thermal properties measurement and discuss the large error sources and ways to reducing them•Provide detailed discussion and review of the spatial resolution of Raman-based temperature measurement•Cover the frontier research on conjugated phonon and hot carrier transfer and how to use Raman spectroscopy to distinguish and characterize them•Critically review the time-domain, frequency domain, and energy transport domain Raman spectroscopies for thermal response and thermal properties characterization•Provide invaluable comments for future Raman development to further improve the accuracy, spatial resolution, and time resolution. Abstract Raman-based thermal characterization is regarded as an invaluable tool in micro/nanoscale heat transfer research, offering exceptional contrast in conjunction with high specificity of noncontact and material specific temperature measurement compared with competing thermometry techniques at the micro/nanoscale. It has been extensively used to determine the thermophysical properties of micro/nanoscale materials. However, for commonly used steady state Raman methods, as two concluded main factors, the temperature coefficients of Raman properties and heating level (or optical absorption) will affect the accuracy of resulting temperature and thermal properties. In this review, we critically discuss the mechanism of Raman spectrum response to temperature and possible error factors in calibration and measurement. In addition, the influence of measurement setup is discussed, and possible technical solutions for improving the measurement accuracy are reviewed. Among noble developments in Raman-based thermal characterizations, the transient heat transfer analysis has been coupled to advances in noncontact Raman-based thermal measurement. By enhancing the temporal and spatial resolution in existing technical conditions, more efficient and accurate transient thermal properties measurement can be realized. Particular attention is paid to the so-called resolved Raman techniques for simultaneous measurement of multiple thermal properties at the micro/nanoscale. In particular, we critically review how these tools can reveal new insights into the complex energy transport processes in 2D semiconductors, which have been impossible to tackle using