Search Results (154)

Ag₂Se has attracted significant attention as a promising alternative to Bi₂Te₃ for near-room-temperature thermoelectric (TE) applications. In this study, flexible Ag₂Se thin films were fabricated via magnetron sputtering under different sputtering power settings, followed by post-deposition annealing to optimize their TE properties. Structural and compositional analyses confirmed the successful synthesis of Ag₂Se films with high crystallinity. Additionally, tuning the sputtering power and annealing temperatures can effectively enhance the electrical conductivity, Seebeck coefficient, and overall power factor. A significant power factor of ~17.4 µW·cm⁻¹·K⁻² at 100 °C was achieved in the 30 W sputtering power and 300 °C annealing sample, pointing out the huge potential of Ag₂Se thin films as self-powered flexible devices. Full article

SnSe₂, as a prominent member of the post-transition metal dichalcogenides, exhibits many intriguing physical phenomena and excellent thermoelectric properties, calling for both fundamental study and potential application in two-dimensional (2D) devices. In this article, we realized the molecular beam epitaxial growth of SnSe₂ films on a $\sqrt{3}\times \sqrt{3}$-Sn reconstructed Si(111) surface. The analysis of reflection high-energy electron diffraction reveals the in-plane lattice orientation as SnSe₂[110]//$\sqrt{3}$-Sn [112]//Si [110]. In addition, the flat morphology of SnSe₂ film was identified by scanning tunneling microscopy (STM), implying the relatively strong adsorption effect of $\sqrt{3}$-Sn/Si(111) substrate to the SnSe₂ adsorbates. Subsequently, the interfacial charge transfer was observed by X-ray photoemission spectroscopy. Afterwards, the direct characterization of electronic structures was obtained via angle-resolved photoemission spectroscopy. In addition to proving the presence of interfacial charge transfer again, a new relatively flat in-gap band was found in monolayer and few-layer SnSe₂, which disappeared in multi-layer SnSe₂. The interface strain-induced partial structural phase transition of thin SnSe₂ films is presumed to be the reason. Our results provide important information on the characterization and effective modulation of electronic structures of SnSe₂ grown on $\sqrt{3}$-Sn/Si(111), paving the way for the further study and application of SnSe₂ in 2D electronic devices. Full article

In-plane thermoelectric thin-film cooling devices are considered a promising solution for thermal management in electronic systems. However, the actual cooling performance is far below that of regular bulk cooling devices, making the design of thin-film devices much more difficult. In this work, a numerical analysis of the cooling performance of single-leg thin-film devices and multi-stage cascaded thin-film devices was conducted to understand the depressed cooling performance. The effects of input current, operating environment, substrate, and contact resistance on cooling performance were investigated and compared with the experimental data. The results show that under ideal conditions, including vacuum environment, absence of substrate, and no contact resistance, the maximum cooling temperature difference simulated by the finite element method (105.4 K) closely matches the theoretical value estimated from the ZT-based calculation (96.6 K). Under practical conditions, such as within atmosphere and with substrate and contact resistance, the simulated maximum temperature difference (2.1 K) fits well with the experimental value (1.1 K). These findings demonstrate that substrate effects, contact resistance, and operating environment can significantly impair the cooling performance of in-plane film thermoelectric devices, although high-performance thermoelectric materials were used. This study provides a guidance for the design and parameter optimization of thermoelectric thin-film cooling modules. Full article

This study presents the calibration methodology of NiCr-NiSi thin-film thermocouples and evaluates their application in real-time temperature monitoring and characterization of fuel cell thermal behavior. Experimental results reveal that the Seebeck coefficients of the NiCr-NiSi thin films remain stable after multiple calibration cycles, indicating good reliability and repeatability. Furthermore, the thermocouples demonstrate an ultrafast response time of less than 15 microseconds and reach thermal equilibrium within 200 microseconds under transient thermal inputs. These characteristics enable accurate and rapid temperature measurement of fuel cell plates up to 100 °C, which is critical for maintaining the safe and efficient operation of fuel cells. Full article

BiCuSeO has emerged as a highly promising material for transverse thermoelectric (TTE) applications, with its performance significantly enhanced through La doping. In this study, we investigate the effect of inclination angle on the TTE performance of inclined Bi_0.94La_0.06CuSeO thin films fabricated using the pulsed laser deposition technique. A huge output voltage of 31.4 V was achieved in the 10° inclined Bi_0.94La_0.06CuSeO film under 308 nm ultraviolet pulsed laser irradiation. Furthermore, the films also exhibited significant response with excellent linearity when exposed to continuous-wave lasers across a broad spectral range (360 nm to 10,600 nm) and a point-like heat source. Notably, the voltage is directly proportional to sin2θ, where θ is the inclination angle. These findings not only provide a clear optimization strategy for TTE performance through inclination angle engineering but also highlight the material’s great potential for developing high-performance optical and thermal sensing TTE devices. Full article

In this work, we developed nanostructured Bi₂Te₃ and Sb₂Te₃ thin films by thermal co-evaporation of their alloys with corresponding pure elements (Bi, Sb, and Te). The films were fabricated on borosilicate glass at different substrate temperatures and deposition rates. At 300 °C, enhanced thermoelectric performance was demonstrated for n-type Bi₂Te₃:Bi and p-type Sb₂Te₃:Te, with Seebeck coefficients of 195 µV K⁻¹ and 178 μV K⁻¹, along with electrical conductivities of 4.6 × 10⁴ (Ω m)⁻¹ and 6.9 × 10⁴ (Ω m)⁻¹, resulting in maximum power factor values of 1.75 mW K⁻² m⁻¹ and 2.19 mW K⁻² m⁻¹, respectively. These values are found to be higher than some reported works in the literature, highlighting the advantage of not introducing additional elements to the system (such as extra doping, which induces complexity to the system). The structural properties, film morphology, and chemical composition of the optimized films were investigated using X-ray diffraction (XRD) and scanning electron microscopy combined with energy-dispersive X-ray spectroscopy (SEM-EDS). The films were found to be polycrystalline with preferred (0 0 6) and (0 1 5) orientations for Bi₂Te₃ and Sb₂Te₃ films, respectively, and stable rhombohedral phases. Additionally, a ring-shaped p-n thermoelectric device for localized heating/cooling was developed and a temperature difference of ~7 °C between the hot and cold zones was obtained using 4.8 mA of current (J = 0.068 mA/mm²). Full article

The objective of our research is to improve the power generation of a thermoelectric generator (TEG) using a single-walled carbon nanotube (SWCNT) sheet by applying the out-of-plane deformation of a slitted kirigami structure. In order to obtain a large amount of power from a TEG using a thin-film thermoelectric (TE) element such as a SWCNT sheet, it is necessary to generate a large temperature difference in the in-plane direction of the thin-film TE element. However, it is difficult to realize a large temperature difference when the thin-film TE element is in contact with a heat source due to the need for a layer with high heat insulation. In this research, we proposed and fabricated a TEG with the out-of-plane deformation of a kirigami structure with slits using a p-n patterned SWCNT sheet as the thin-film TE material and evaluated the open circuit voltage with respect to the out-of-plane deformation and the number of TE elements. As a result, the output performance of SWCNT TEG was clarified when the out-of-plane deformation and the number of TE element pairs were varied. Full article

In the present study, for the first time, aluminum-doped zinc oxide (AZO) thin films with nanoinclusions of amorphous carbon have been synthesized via spin coating, and the thermoelectric performances were investigated varying the aging period of the solution, the procedure of carbon nanoparticles’ addition, and the annealing atmosphere. The addition of nanoparticles has been pursued to introduce phonon scattering centers to reduce thermal conductivity. All the samples showed a strong orientation along the [002] crystallographic direction, even though the substrate is amorphous silica, with an intensity of the diffraction peaks reaching its maximum in samples annealed in the presence of hydrogen, and generally decreasing by the addition of carbon nanoparticles. Absolute values of the Seebeck coefficient improve when nanoparticles are added. At the same time, electric conductivity is higher for the sample with 1 wt.% of carbon and annealed in Ar with 1% of H₂, both increasing in absolute value with the temperature rise. Among all the samples, the lowest thermal conductivity value of 1.25 W/(m∙K) was found at room temperature, and the highest power factor was 111 μW/(m∙K²) at 325 °C. Thus, the introduction of carbon effectively reduced thermal conductivity, while also increasing the power factor, giving promising results for the further development of AZO-based materials for thermoelectric applications. Full article

After the deposition process, the lattice structure of doped germanium remains low. Post-processing annealing reorders the structure and increases the output parameters. Thin films of germanium doped with gold (Ge:Au) and vanadium (Ge:V) were magnetron-sputtered on glass substrates. The course of the activation process was monitored in situ. Two different methods of post-processing thermal activation of the films were studied. The first method was to place the structure at an elevated temperature for a specified period of time. The second method involved placing the structure on a heating table and cycling the heating and cooling several times from room temperature to about 823 K. Both methods fulfill their function well. The differences come down to research aspects. The best thermoelectric parameters were achieved for germanium doped with 0.95 at.% vanadium. The Seebeck coefficient of 212 μV/K and the power factor of 1.24 mW·m⁻¹·K⁻² were obtained at 500 K. Full article

Nowadays, polycrystalline lead telluride is one of the premier substances for thermoelectric devices while remaining a hopeful competitor to current semiconductor materials used in mid-infrared photonic applications. Notwithstanding that, the development of reliable and reproducible routes for the synthesis of PbTe thin films has not yet been accomplished. As an effort toward this aim, the present article reports progress in the growth of polycrystalline indium-doped PbTe films and their study. The introduction foregoing the main text presents an overview of studies in these and closely related research fields for seven decades. The main text reports on the electron-beam-assisted physical vapor deposition of n-type indium-doped PbTe films on two different amorphous substrates. This doping of PbTe is unique since it sets electron density uniform over grains due to pinning the Fermi level. In-house optimized parameters of the deposition process are presented. The films are structurally characterized by a set of techniques. The transport properties of the films are measured with the original setups described in detail. The infrared transmission spectra are measured and simulated with the original optical-multilayer modeling tool described in the appendix. Conclusions of films’ quality in terms of these properties altogether are drawn. Full article

In the assembly process of aerospace parts, drilling is essential for carbon fiber-reinforced materials. However, due to the extreme thermal sensitivity of these composites, continuous drilling often leads to irreparable defects such as hole wall burns and exit delamination caused by concentrated cutting heat, resulting in the scrapping of parts. To address this issue, this paper explores the impact of temperature characteristics on drilling quality, providing guidance for optimizing the composite drilling process. A simulation model for single and continuous drilling was established to analyze the temperature distribution on the tool surface during drilling. A drilling temperature measurement system based on thin-film thermocouple technology was developed, enabling real-time online temperature monitoring. Continuous drilling experiments were conducted, analyzing the correlation between maximum drilling temperature and hole quality. Results show that temperatures from −25.75 °C to −9.75 °C and from 182 °C to 200.75 °C cause significant exit damage, while optimal hole quality is achieved between −1.25 °C and 168 °C. Full article

Providing self-powered energy for wearable electronic devices is currently an important research direction in the field of thermoelectric (TE) thin films. In this study, a simple dual-source magnetron sputtering method was used to prepare Ag₂Te thin films, which exhibit good TE properties at room temperature, and the growth temperature and subsequent annealing process were optimized to obtain high-quality films. The experimental results show that films grown at a substrate temperature of 280 °C exhibit a high power factor (PF) of ~3.95 μW/cm·K² at room temperature, which is further improved to 4.79 μW/cm·K² after optimal annealing treatment, and a highest PF of ~7.85 μW/cm·K² was observed at 200 °C. Appropriate annealing temperature effectively increases the carrier mobility of the Ag₂Te films and adjusts the Ag/Te ratio to make the composition closer to the stoichiometric ratio, thus promoting the enhancement of electrical transport properties. A TE device with five legs was assembled using as-fabricated Ag₂Te thin films. With a temperature difference of 40 K, the device was able to generate an output voltage of approximately 14.43 mV and a corresponding power of about 50.52 nW. This work not only prepared a high-performance Ag₂Te film but also demonstrated its application prospects in the field of self-powered electronic devices. Full article

The aim of this work was to investigate the possibility of modifying the physical properties of indium tin oxide (ITO) layers by annealing them in different atmospheres and temperatures. Samples were annealed in vacuum, air, oxygen, nitrogen, carbon dioxide and a mixture of nitrogen with hydrogen (NHM) at temperatures from 200 °C to 400 °C. Annealing impact on the crystal structure, optical, electrical, thermal and thermoelectric properties was examined. It has been found from XRD measurements that for samples annealed in air, nitrogen and NHM at 400 °C, the In₂O₃/In₄Sn₃O₁₂ share ratio decreased, resulting in a significant increase of the In₄Sn₃O₁₂ phase. The annealing at the highest temperature in air and nitrogen resulted in larger grains and the mean grain size increase, while vacuum, NHM and carbon dioxide atmospheres caused the decrease in the mean grain size. The post-processing in vacuum and oxidizing atmospheres effected in a drop in optical bandgap and poor electrical properties. The carbon dioxide seems to be an optimal atmosphere to obtain good TE generator parameters—high ZT. The general conclusion is that annealing in different atmospheres allows for controlled changes in the structure and physical properties of ITO layers. Full article

Cu₂Se is an attractive thermoelectric material due to its layered structure, low cost, environmental compatibility, and non-toxicity. These traits make it a promising replacement for conventional thermoelectric materials in large-scale applications. This study focuses on preparing Cu₂Se flexible thin films through in situ magnetron sputtering technology while carefully optimizing key preparation parameters, and explores the physical mechanism of thermoelectric property enhancement, especially the power factor. The films are deposited onto flexible polyimide substrates. Experimental findings demonstrate that films grown at a base temperature of 200 °C exhibit favorable performance. Furthermore, annealing heat treatment effectively regulates the Cu element content in the film samples, which reduces carrier concentration and enhances the Seebeck coefficient, ultimately improving the power factor of the materials. Compared to the unannealed samples, the sample annealed at 300 °C exhibited a significant increase in room temperature Seebeck coefficient, rising from 9.13 μVK⁻¹ to 26.73 μVK⁻¹. Concurrently, the power factor improved from 0.33 μWcm⁻¹K⁻² to 1.43 μWcm⁻¹K⁻². Full article