Raman-based Nanoscale Thermal Transport Characterization: A Critical Review

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 traditional tools. Considering its precision and sensitivity, there is still a large room for development of Raman techniques for the investigation of complex and coupled heat transfer process in low dimensions and new materials.