arXiv2026
As semiconductor devices shrink toward the nanoscale, heat transport and thermal-energy-storage behavior in materials and interfaces become increasingly dependent on length scale, structure, and interfaces. Accurate characterization of thermophysical properties, including thermal conductivity, interfacial thermal conductance, and volumetric heat capacity, is therefore essential for functional-material design and thermal management of advanced electronic devices. Photothermal thermoreflectance techniques provide noncontact measurements with high spatial and temporal resolution and a broad measurement range, making them important tools for micro- and nanoscale thermophysical characterization. This review examines the physical principles and technical characteristics of transient thermoreflectance (TTR), time-domain thermoreflectance (TDTR), frequency-domain thermoreflectance (FDTR), steady-state thermoreflectance (SSTR), spatial-domain thermoreflectance (SDTR), and the square-pulsed source (SPS) method. A unified heat-diffusion framework is established to compare these methods in terms of parameter sensitivity, measurement uncertainty, and applicability. Representative applications illustrate their suitability for low-thermal-conductivity materials, anisotropic films, crystalline materials, and multilayer heterostructures, as well as their complementary capabilities for characterizing thin-film thermal conductivity, interfacial thermal conductance, and in-plane/cross-plane heat transport. Finally, emerging directions are discussed, including ultrahigh spatiotemporal resolution, multiphysics coupling, in-line industrial inspection, intelligent data processing, and natural-language-driven analysis.