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    Advances in flexible telluride thin-film thermoelectric generators: Deposition, performance, and module fabrication
    (2026-04-01)
    Theekhasuk, Nattharika
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    Kianwimol, Supasak
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    Khumtong, Thanakorn
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    Toan, Nguyen Van
    Flexible thermoelectric generators (TEGs) are gaining increasing attention for wearable and skin-attachable electronics due to their ability to harvest low-grade heat from the human body. In this work, p-type Sb<inf>2</inf>Te<inf>3</inf> and n-type Bi<inf>2</inf>Te<inf>3</inf> thin films were deposited by direct current (DC) magnetron sputtering, and the effects of post-deposition annealing on their structural, electrical, and thermal transport properties were systematically evaluated. X-ray diffraction revealed that n-Bi<inf>2</inf>Te<inf>3</inf> exhibited higher crystallinity than p-Sb<inf>2</inf>Te<inf>3</inf>, attributed to its lower formation energy. Annealing at 250 °C markedly enhanced the electrical conductivity of both films, with p-Sb<inf>2</inf>Te<inf>3</inf> showing a larger improvement due to concurrent increases in carrier concentration and mobility driven by Te volatilization and the formation of acceptor-type vacancies and antisite defects. In contrast, n-Bi<inf>2</inf>Te<inf>3</inf> exhibited a slight reduction in carrier concentration as a result of compensating donor defects. Consequently, maximum ZT values of approximately 0.5 for p-Sb<inf>2</inf>Te<inf>3</inf> and 0.25 for n-Bi<inf>2</inf>Te<inf>3</inf> were achieved at 513 K. Notably, the compatibility factor (S) values of both films differed by less than a factor of two, indicating favorable thermodynamic pairing for p–n module assembly. A flexible TEG module with 12 thermocouples was subsequently fabricated and delivered an output power of 0.65 μW at ΔT < 25 K, demonstrating promising potential for scalable self-powered wearable electronics.
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    Structural, morphological and adhesion properties of coFeB thin films deposited by DC magnetron sputtering
    (2013-10-29)
    Ibuki, Chuleerat
    ;
    In this work the effects of amorphous (glass) and crystalline (Si) substrates on the structural, morphological and adhesion properties of CoFeB thin film deposited by DC Magnetron sputtering were investigated. It was found that the structure of a substrate affects to crystal formation, surface morphology and adhesion of CoFeB thin films. The X-Ray diffraction patterns reveal that as-deposited CoFeB thin film at low sputtering power was amorphous and would become crystal when the power increased. The increase in crystalline structure of CoFeB thin film is attributed to the crystalline substrate and the increase of kinetic energy of sputtering atoms. Atomic Force Microscopy images of CoFeB thin film clearly show that the roughness, grain size, and uniformity correlate to the sputtering power and the structure of substrate. The CoFeB thin film on glass substrate shows a smooth surface and a small grain size whereas the CoFeB thin film on Si substrate shows a rough surface and a slightly increases of grain size. Sticky Tape Test on CoFeB thin film deposited on glass substrate indicates the adhesion failure with a high sputtering power. The results suggest that the crystalline structure of substrate affects to the atomic bonding and the sputtering power affects to intrinsic stress of CoFeB thin film. © (2013) Trans Tech Publications, Switzerland.
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    Enhancing the thermoelectric properties of sputtered Sb2Te3 thick films via post-annealing treatment
    (2020-04-15)
    Junlabhut, Prasopporn
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    Nuthongkum, Pilaipon
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    Harnwunggmoung, Adul
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    Sb<inf>2</inf>Te<inf>3</inf> films of more than 10 μm in thickness were deposited on flexible polyimide substrates by heat treatment-assisted DC magnetron sputtering. The post-annealing parameters including the temperature (150–350 °C) and time (15–60 min) were varied to investigate the microstructure, chemical composition, porosity and thermoelectric properties of the thick films. X-ray diffraction showed that both the as-deposited and post-annealed films were polycrystalline with significant preferential growth along the (015) plane. The films showed slightly off-stoichiometric compositions after post-annealing treatment. Increasing the annealing temperature and annealing time led to an increase in crystalline size and a decrease in porosity of the thick films. This was related to grain growth, agglomeration and surface improvement. The electrical transport and thermoelectric properties including carrier concentration, carrier mobility, electrical conductivity and Seebeck coefficient were investigated using Hall effect measurements and a ZEM-3 apparatus. A maximum power factor of 1.7 mW/K<sup>2</sup>m was obtained following annealing at 350 °C for 30 min.
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    Influence of Sputtering Power Density on the Thermoelectric and Mechanical Properties of Flexible Thermoelectric Antimony Telluride Films Deposited by DC Magnetron Sputtering
    (2020-05-01)
    Junlabhut, Prasopporn
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    Nuthongkum, Pilaipon
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    Harnwunggmoung, Adul
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    Antimony telluride (Sb<inf>2</inf>Te<inf>3</inf>) films were deposited on flexible polyimide substrates by DC magnetron sputtering technique using a 99.9% alloy Sb<inf>2</inf>Te<inf>3</inf> target. We measured structural, electrical, thermoelectric and mechanical properties with sputtering power density in the range 30–50 W. X-ray diffraction confirmed that all Sb<inf>2</inf>Te<inf>3</inf> films have high crystallinity with a significant preferential growth along the (015) plane. Surface morphologies were verified by scanning electron microscope: deposited film grain size increased with sputtering power density. The elemental composition was determined by energy dispersive x-ray spectroscopy. Electrical transport properties, carrier concentration, was measured by Hall effect measurement at room temperature. Electrical conductivity and Seebeck coefficient were simultaneously measured by a DC four-terminal method (ZEM-3). The power factor was strongly dominated by electrical conductivity, leading to a maximum of 1.95 mW/K<sup>2</sup>m with sputtering power 45 W at 300°C. The wettability test, based on the contact angle, evaluated surface energy and hydrophilicity. Nanoindentation was measured on a NHT<sup>2</sup> CSM Instrument with diamond Berkovich indenter (B-P 31) at room temperature. The hardness and elastic modulus of deposited Sb<inf>2</inf>Te<inf>3</inf> films increased with the power density.
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