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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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Sakdanuphab, Rachsak
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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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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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Sakdanuphab, Rachsak
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Harnwunggmoung, Adul
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Sakulkalavek, Aparporn
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/K2m 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 NHT2 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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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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Sakulkalavek, Aparporn
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Harnwunggmoung, Adul
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Limsuwan, Pichet
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/K2m was obtained following annealing at 350 °C for 30 min.
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Effect of sputtering power on optical properties of nickel oxide electrochromic thin films
(2020-01-01)
Panprom, P.
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Sritonwong, P.
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Limwichian, S.
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Eiamchai, P.
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Patthanasettakul, V.
The preparation and characterization of nickel oxide (NiO) thin film for electrochromic smart window applications are studied. The NiO thin film was prepared by the DC magnetron sputtering from a pure nickel target. The sputtering power was varies in the interval 50–200 W. The crystallinity and physical morphology of NiO films are characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM), respectively. The XRD result revealed that polycrystalline NiO thin films with preferred growth directions along (111) and (200) planes are obtained. Moreover, the electrochromic property of NiO thin films was investigated with a UV-Visible spectrophotometer. The colored state of the electrochromic cell was obtained by the ion insertion at the 1-V external applied bias in 0.1 M KOH. The reversibility between the colored and bleached states is confirmed by the optical transmittance. The result shows the optical contrast as high as 28.68.
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Effect of operated pressure on anticorrosive behavior of Ta2O5 thin film grown by D.C. reactive magnetron sputtering system
(2013-10-29)
Khemasiri, Narathon
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Chananonnawathorn, Chanunthorn
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Horprathum, Mati
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Rayanasukha, Yossawat
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Phromyothin, Darinee
Tantalum oxide (Ta<inf>2</inf>O<inf>5</inf>) thin films, 100 nm thick were deposited by D.C. reactive magnetron sputtering system at different operated pressure on unheated p-type silicon (100) wafer and 304 stainless substrates. Their crystalline structure, film surface morphology and optical properties, as well as anticorrosive behavior, were investigated. The structure and morphology of films were characterized by grazing-incidence X-ray diffraction (GIXRD) and atomic force microscopy (AFM). The optical properties were determined by spectroscopic ellipsometry (SE). The corrosion performances of the films were investigated through potentiostat and immersion tests in 1 M NaCl solutions. The results showed that as-deposited Ta<inf>2</inf>O<inf>5</inf> thin films were amorphous. The refractive index varied from 2.06 to 2.17 (at 550 nm) with increasing operated pressure. The corrosion rate of Ta<inf>2</inf>O<inf>5</inf> thin film improves as the operated pressure decreases. The Ta<inf>2</inf>O<inf>5</inf> thin films deposited at 3 mTorr operated pressure could be exhibited high performance anticorrosive behavior. © (2013) Trans Tech Publications, Switzerland.
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Structural, morphological and adhesion properties of coFeB thin films deposited by DC magnetron sputtering
(2013-10-29)
Ibuki, Chuleerat
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Sakdanuphab, Rachasak
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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The optimization of TiN film deposited by DC magnetron sputtering provided for Al diffusion barrier
(2010-02-05)
Pankiew, A.
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Bunjongpru, W.
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Somwang, N.
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Porntheeraphat, S.
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Pratontep, S.
Titanium nitride (TiN) film has been widely used as a diffusion barrier layer for VLSI contact metallization because TiN is an excellent barrier against inter-diffusion between Al and Si substrate or silicide. In this work, we studied the properties of TiN films deposited by DC magnetron sputtering with varying N<inf>2</inf>:Ar flow rate ratio in order to optimize growth conditions and film properties provided for Al diffusion barrier purpose. The TiN films were deposited at the constant pressure level and sputtering time. The crystalline orientation, composition and electrical properties of deposited TiN films were characterized by XRD, AES-depth profile and Four Point Probe measurement, respectively. The XRD results show that the deposited TiN film has two preferred orientations of TiN(111) and TiN(200) planes. The highest intensity of the TiN(111) plane was obtained when the N<inf>2</inf>:Ar flow rate ratio was 3:1. The electrical resistivity was increased when the N <inf>2</inf>:Ar flow rate ratio was decreased. The minimum electrical resistivity is 127.8 μΩ-cm when the N<inf>2</inf>:Ar flow rate ratio is 3:1. © (2010) Trans Tech Publications.

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