The photothermal phenomenon involves material photon heating in the form of continuous waves, modulated waves, or pulses. The resulting temperature rise carries very rich information about the material's structures and thermophysical properties. This review is constructed to cover some of the extended ideas of the photothermal phenomenon for measuring a material's thermophysical properties and interface thermal conductance/resistance. For frequency-domain photothermal phenomena, the photoacoustic (PA) and photothermal radiation (PT) techniques provide great ways to measure coatings and suspended samples, which can also be measured using the laser flash and time-domain thermoreflectance (TDTR) techniques. Thermal probing based on electrical thermal sensing is successfully implemented in the transient photo-electro-thermal (TPET) and pulsed laser-assisted thermal relaxation (PLTR) techniques, which significantly extend the capability of laser flash technique to micro/nanoscale 1D structures. The energy transport state-resolved Raman (ET-Raman) is distinct from traditional techniques in its material-specific thermal sensing capability and integral way of ultrafast thermal sensing. Detailed physics discussions are provided for all these techniques, including their advantages and limitations. Still, large development rooms exist for the relatively new techniques, including TPET, PLTR, and ET-Raman. These include measurements under extreme situations, sensitivity improvement, and distinguishing conjugated physical processes.

The discovery of graphene and its analog, such as MoS_2, has boosted research. The thermal transport in 2D materials gains much of the interest, especially when graphene has high thermal conductivity. However, the thermal properties of 2D materials obtained from experiments have large discrepancies. For example, the thermal conductivity of single layer suspended graphene obtained by experiments spans over a large range: 1100–5000 W/m·K. Apart from the different graphene quality in experiments, the thermal characterization methods play an important role in the observed large deviation of experimental data. Here we provide a critical review of the widely used thermal characterization techniques: the optothermal Raman technique and the micro-bridge method. The critical issues in the two methods are carefully revised and discussed in great depth. Furthermore, improvements in Raman-based techniques to investigate the energy transport in 2D materials are discussed.

The extremely small size of micro-/nanomaterials limits the application of conventional thermal measurement methods using a contact heating source or probing sensor. Therefore, non-contact thermal measurement methods are preferable in micro-/nanoscale thermal characterization. In this review, one of the non-contact thermal measurement methods, photothermal (PT) technique based on thermal radiation, is introduced. When subjected to laser heating with controllable modulation frequencies, surface thermal radiation carries fruitful information for thermal property determination. As thermal properties are closely related to the internal structure of materials, for micro-/nanomaterials, PT technique can measure not only thermal properties but also features in the micro-/nanostructure. Practical applications of PT technique in the thermal measurement of micro-/nanomaterials are then reviewed, including special wall-structure investigation in multiwall carbon nanotubes, porosity determination in nanomaterial assemblies, and the observation of amorphous/crystalline structure transformation in proteins in heat treatment. Furthermore, the limitations and future application extensions are discussed.

Spin–orbit torques (SOTs) in compensated ferrimagnets (FMs) have been widely studied due to their abundant advantages for the application in spintronic devices. Recently, the SOT in FM metals near compensation tuned by composition and temperature has been reported. However, the SOT in FM insulators (FMIs) near compensation still remains elusive. In this work, we report the study of the SOT in FMI near compensation tuned by the temperature. First, Pt/Gd₃Fe₅O₁₂ (GdIG) bilayer films with high crystallinity and perpendicular magnetic anisotropy were fabricated by magnetron sputtering. Then, the SOT was measured by varying the temperature. It is found that the SOT generation is drastically enhanced close to the compensation temperature, which is verified to be caused by the decrease in the net magnetization. The effective spin Hall angle in Pt/GdIG bilayer films is estimated to be ∼0.0073, which is almost independent of the temperature. Our study provides a potential approach in emerging FMIs for spintronic devices with low-energy consumption.

Organic-inorganic halide perovskites have demonstrated preeminent optoelectronic performance in recent years due to their unique material properties, and have shown great potential in the field of photodetectors. In this study, a coupled opto-electronic model is constructed to reveal the hidden mechanism of enhancing the performance of perovskite photodetectors that are suitable for both inverted and regular structure doped p-i-n perovskite photodiodes. Upon illumination, the generation rate of photogenerated carriers is calculated followed by carrier density distribution, which serves as a coupled joint to further analyze the recombination rate, electric field strength, and current density of carriers under different doping types and densities. Moreover, experiments were carried out in which the doping types and densities of the active layer were regulated by changing the precursor ratios. With optimal doping conditions, the inverted and regular perovskite photodiodes achieved an external quantum efficiency of 74.83% and 73.36%, and a responsivity of 0.417 and 0.404 A/W, respectively. The constructed coupled opto-electronic model reveals the hidden mechanism and along with the doping strategy, this study provides important guidance for further analysis and improvement of perovskite-based photodiodes.