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The flash methods, which are the most popular transient methods for measuring the thermal diffusivity of solid materials, have evolved into ultrafast laser flash methods by using picosecond or nanosecond pulse lasers as a heating source and a thermo-reflectance technique such as high-speed thermometry. In conventional ultrafast laser flash methods, thermal diffusivity is determined by fitting an analytical equation after single pulse heating to observe thermo-reflectance signals, although actual thermo-reflectance signals are observed after periodic pulse heating. This paper presents an exact analytical solution of the temperature response expressed by Fourier series for one-dimensional heat diffusion after periodic pulse heating. These Fourier coefficients are directly related to the Laplace transformation of the temperature response after single pulse heating. The signal observed for a 100 nm thick platinum thin film on a fused quartz substrate was analyzed by this Fourier expansion analysis and fitted by analytical equations with three parameters: heat diffusion time across thin film, the ratio of heat effusion of the substrate to thin film, and the amplitude of the signal over the entire range of pulse interval in the time domain. Robustness in determining the thermal diffusivity of the thin film by the ultrafast laser flash method can be improved by this new analysis approach. [ABSTRACT FROM AUTHOR]

In this work, we present the influence of Ga doping in Mg2Sn thin epitaxial films on sapphire (0001) substrates. Our results suggest that epitaxial nature is essential for achieving high mobility. Furthermore, we found that Ga incorporation influences the carrier concentration and acts as a phonon-scattering center. The optimal power factor and figure of merit values obtained were 1.49 × 10−3 W·m−1·K−1 and 0.08 at 300 K for Mg2Sn0.97Ga0.03. The values are in the same range as the bulk material of Mg-based II–IV semiconductors, suggesting that the combination of doping and epitaxial nature in thin films can be a promising route for miniaturization of thermoelectric devices based on Mg-based materials. [ABSTRACT FROM AUTHOR]

The reciprocity of heat transfer is a fundamental principle. However, there are few experimental studies to verify this principle. In this paper, we measured two layer samples made of ordinary metal by the laser flash method to verify the reciprocity principle. We heated and detected the different surfaces of each two layer sample to observe the reciprocal response. We also made use of areal heat diffusion time to analyze the temperature rise of two layer samples to enable to extend analysis for future multi-layer samples. This study is an important starting point to discuss whether characteristic materials obey the reciprocal principle. [ABSTRACT FROM AUTHOR]

Investigates the negative ion beam modification of the biocompatibility of polystyrene surface. Artificial formation of neuron network in culture; Negative-ion implantation into polystyrene; In vitro cells of rat adrenal pheochromocytoma.