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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]

The crystallographic and transport properties of thin films fabricated by pulsed laser deposition and belonging to the Sm y (Fe x Ni1- x )4Sb12 filled skutterudite system were studied with the aim to unveil the effect exerted by temperature and duration of thermal treatments on structural and thermoelectric features. The importance of annealing treatments in Ar atmosphere up to 523 K was recognized, and the thermal treatment performed at 473 K for 3 h was selected as the most effective in improving the material properties. With respect to the corresponding bulk compositions, a significant enhancement in phase purity, as well as an increase in electrical conductivity and a drop in room temperature thermal conductivity, were observed in annealed films. The low thermal conductivity, in particular, can be deemed as deriving from the reduced dimensionality and the consequent substrate/film interfacial stress, coupled with the nanometric grain size. [ABSTRACT FROM AUTHOR]

SiGe‐based thermoelectric (TE) materials are well‐known for high‐temperature utilization, but rarely relevant in the low temperature region. Here a Ge quantum dots (QDs) and Sn precipitation SiGeSn hybrid film are constructed via ultrafast high temperature annealing (UHA) of a treated P‐ion implantation SiGeSn film on Si/SiO2 substrate. Combining the modulation doping effect dominated by Sn precipitates and the energy filtering effect caused by Ge QDs, the optimized SiGe films achieve a giant power factor as high as 91 µW cm−1 K−2 @300 K, room temperature, while maintaining low thermal conductivity. This strategy on film construction provides a novel insight for TE materials with striking performance. [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]

Filled skutterudites are currently studied as promising thermoelectric materials due to their high power factor and low thermal conductivity. The latter property, in particular, can be enhanced by adding scattering centers, such as the ones deriving from low dimensionality and the presence of interfaces. This work reports on the synthesis and characterization of thin films belonging to the Smy(FexNi1−x)4Sb12-filled skutterudite system. Films were deposited under vacuum conditions by the pulsed laser deposition (PLD) method on fused silica substrates, and the deposition temperature was varied. The effect of the annealing process was studied by subjecting a set of films to a thermal treatment for 1 h at 423 K. Electrical conductivity σ and Seebeck coefficient S were acquired by the four-probe method using a ZEM-3 apparatus performing cycles in the 348–523 K temperature range, recording both heating and cooling processes. Films deposited at room temperature required three cycles up to 523 K before being stabilized, thus revealing the importance of a proper annealing process in order to obtain reliable physical data. XRD analyses confirm the previous result, as only annealed films present a highly crystalline skutterudite not accompanied by extra phases. The power factor of annealed films is shown to be lower than in the corresponding bulk samples due to the lower Seebeck coefficients occurring in films. Room temperature thermal conductivity, on the contrary, shows values comparable to the ones of doubly doped bulk samples, thus highlighting the positive effect of interfaces on the introduction of scattering centers, and therefore on the reduction of thermal conductivity. [ABSTRACT FROM AUTHOR]

The crystallographic and transport properties of thin films fabricated by pulsed laser deposition and belonging to the Sm y (Fe x Ni 1- x ) 4 Sb 12 filled skutterudite system were studied with the aim to unveil the effect exerted by temperature and duration of thermal treatments on structural and thermoelectric features. The importance of annealing treatments in Ar atmosphere up to 523 K was recognized, and the thermal treatment performed at 473 K for 3 h was selected as the most effective in improving the material properties. With respect to the corresponding bulk compositions, a significant enhancement in phase purity, as well as an increase in electrical conductivity and a drop in room temperature thermal conductivity, were observed in annealed films. The low thermal conductivity, in particular, can be deemed as deriving from the reduced dimensionality and the consequent substrate/film interfacial stress, coupled with the nanometric grain size., (© 2023 IOP Publishing Ltd.)

The effect of SnO 2 addition (0, 1, 2, 4 wt.%) on thermoelectric properties of c -axis oriented Al-doped ZnO thin films (AZO) fabricated by pulsed laser deposition on silica and Al 2 O 3 substrates was investigated. The best thermoelectric performance was obtained on the AZO + 2% SnO 2 thin film grown on silica, with a power factor ( PF ) of 211.8 μW/m·K 2 at 573 K and a room-temperature (300 K) thermal conductivity of 8.56 W/m·K. PF was of the same order of magnitude as the value reported for typical AZO bulk material at the same measurement conditions (340 μW/m·K 2 ) while thermal conductivity κ was reduced about four times.