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  • 1.
    Ali, Sharafat
    et al.
    Linnaeus University, Sweden; Corning Inc, NY 14831 USA.
    Paul, Biplab
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Magnusson, Roger
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Broitman, Esteban
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Jonson, Bo
    Linnaeus University, Sweden.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Synthesis and characterization of the mechanical and optical properties of Ca-Si-O-N thin films deposited by RF magnetron sputtering2017In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 315, p. 88-94Article in journal (Refereed)
    Abstract [en]

    Ca-Si-O-N thin films were deposited on commercial soda-lime silicate float glass, silica wafers and sapphire substrates by RF magnetron co-sputtering from Ca and Si targets in an Ar/N-2/O-2 gas mixture. Chemical composition, surface morphology, hardness, reduced elastic modulus and optical properties of the films were investigated using X-ray photoelectron spectroscopy, scanning electron microscopy, nanoindentation, and spectroscopic ellipsometry. It was found that the composition of the films can be controlled by the Ca target power, predominantly, and by the reactive gas flow. Thin films in the Ca-Si-O-N system are composed of N and Ca contents up to 31 eq. % and 60 eq. %, respectively. The films thickness ranges from 600 to 3000 nm and increases with increasing Ca target power. The films surface roughness varied between 2 and 12 nm, and approximately decreases with increasing power of Ca target. The hardness (4-12 GPa) and reduced elastic modulus (65-145 GPa) of the films increase and decrease with the N and Ca contents respectively. The refractive index (1.56-1.82) is primarily dictated by the N content. The properties are compared with findings for bulk glasses in the Ca-Si-(Al)-O-N systems, and it is concluded that Ca-Si-O-N thin films have higher values of hardness, elastic modulus and refractive index than bulk glasses of similar composition. (C) 2017 Elsevier B.V. All rights reserved.

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  • 2.
    Ali, Sharafat
    et al.
    Linnaeus Univ, Sweden.
    Paul, Biplab
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Magnusson, Roger
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Ekström, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Pallier, Camille
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. RISE IVF, S-58188 Linkoping, Sweden.
    Jonson, Bo
    Linnaeus Univ, Sweden.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Optical and mechanical properties of amorphous Mg-Si-O-N thin films deposited by reactive magnetron sputtering2019In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 372, p. 9-15Article in journal (Refereed)
    Abstract [en]

    In this work, amorphous thin films in Mg-Si-O-N system typically containing amp;gt; 15 at.% Mg and 35 at.% N were prepared in order to investigate especially the dependence of optical and mechanical properties on Mg composition. Reactive RF magnetron co-sputtering from magnesium and silicon targets were used for the deposition of Mg-Si-O-N thin films. Films were deposited on float glass, silica wafers and sapphire substrates in an Ar, N-2 and O-2 gas mixture. X-ray photoelectron spectroscopy, atomic force microscopy, scanning electron microscopy, spectroscopic ellipsometry, and nanoindentation were employed to characterize the composition, surface morphology, and properties of the films. The films consist of N and Mg contents up to 40 at.% and 28 at.%, respectively and have good adhesion to substrates and are chemically inert. The thickness and roughness of the films increased with increasing content of Mg. Both hardness (16-21 GPa) and reduced elastic modulus (120-176 GPa) are strongly correlated with the amount of Mg content. The refractive index up to 2.01 and extinction coefficient up to 0.18 were found to increase with Mg content. The optical band gap (3.1-4.3) decreases with increasing the Mg content. Thin film deposited at substrate temperature of 100 degrees C shows a lower value of hardness (10 GPa), refractive index (1.75), and higher values of reduced elastic modulus (124 GPa) as compared to the thin film deposited at 310 degrees C and 510 degrees C respectively, under identical synthesis parameters.

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  • 3.
    Ali, Sharafat
    et al.
    Linnaeus University, Sweden.
    Paul, Biplab
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Magnusson, Roger
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, Faculty of Science & Engineering.
    Greczynski, Grzegorz
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Broitman, Esteban
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Jonson, Bo
    Linnaeus University, Sweden.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Novel transparent Mg-Si-O-N thin films with high hardness and refractive index2016In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 131Article in journal (Refereed)
    Abstract [en]

    There is an increasing demand for glass materials with better mechanical and optical properties for display and electronic applications. This paper describes the deposition of novel thin films of Mg-circle divide-Si-O-N onto float glass substrates. Amorphous thin films in the Mg-Si-O-N system with high nitrogen and magnesium contents were deposited by reactive RF magnetron co-sputtering from Mg and Si targets in Ar/N-2/O-2 gas mixtures. The thin films studied span an unprecedented range of compositions up to 45 at% Mg and 80 at% N out of cations and anions respectively. Thin films in the Mg-Si-O-N system were found to be homogeneous and transparent in the visible region. Mechanical properties like hardness (H) and reduced elastic modulus (Er) show high values, up to 21 GPa and 166 GPa respectively. The refractive index (1.87-2.00) increases with increasing magnesium and nitrogen contents. (C) 2016 Elsevier Ltd. All rights reserved.

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  • 4.
    Alijan Farzad Lahiji, Faezeh
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Bairagi, Samiran
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Magnusson, Roger
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Sortica, Mauricio A.
    Uppsala Univ, Sweden.
    Primetzhofer, Daniel
    Uppsala Univ, Sweden.
    Ekström, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Paul, Biplab
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Le Febvrier, Arnaud
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Growth and optical properties of NiO thin films deposited by pulsed dc reactive magnetron sputtering2023In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 41, no 6, article id 063402Article in journal (Refereed)
    Abstract [en]

    NiO thin films with varied oxygen contents are grown on Si(100) and c-Al2O3 at a substrate temperature of 300 degrees C using pulsed dc reactive magnetron sputtering. We characterize the structure and optical properties of NiO changes as functions of the oxygen content. NiO with the cubic structure, single phase, and predominant orientation along (111) is found on both substrates. X-ray diffraction and pole figure analysis further show that NiO on the Si(100) substrate exhibits fiber-textured growth, while twin domain epitaxy was achieved on c-Al2O3, with NiO(111) k Al2O3(0001) and NiO[1 (1) over bar0]k Al2O3[10 (1) over bar0] or NiO[(1) over bar 10]k Al2O3[2 (1) over bar(1) over bar0] epitaxial relationship. The oxygen content in NiO films did not have a significant effect on the refractive index, extinction coefficient, and absorption coefficient. This suggests that the optical properties of NiO films remained unaffected by changes in the oxygen content.

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  • 5.
    Alijan Farzad Lahiji, Faezeh
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Paul, Biplab
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Le Febvrier, Arnaud
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Unusual tilted growth and epitaxial relationship of NaCl B1-structured NiO and CrN on r-plane Al2O32024In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 135, no 6, article id 065302Article in journal (Refereed)
    Abstract [en]

    Epitaxial NiO and CrN thin films were deposited on a single-crystal Al2O3(11¯02) (r-plane sapphire) using magnetron sputtering. The two materials were intentionally deposited into two different deposition chamber designs and under different conditions (temperature, pressure, gases, and energy of sputtered particles). Despite the differences in the deposition condition and material system, both materials had the same feature with uncommon tilted epitaxial growth. Through an in-depth x-ray diffraction analysis of the NaCl (B1)-structured materials on r-plane sapphire, the full twin domain epitaxial relations were determined and can be described as (110)NaCl(B1)∥(44¯03)Al2O3 and [11¯2]NaCl(B1)∥[1¯1¯20]Al2O3⁠. This relationship differs from the previously observed orientation of (100)NaCl(B1)∥(11¯02)Al2O3 and [100]NaCl(B1)∥[101¯0]Al2O3⁠. These results are of general relevance for the growth of the extended NaCl (B1)-structured cubic material family onto a r-plane sapphire substrate where similar epitaxial growth can be expected.

  • 6.
    Du, Yong
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Shanghai Inst Technol, Peoples R China.
    Chen, Jiageng
    Shanghai Inst Technol, Peoples R China.
    Liu, Xin
    Shanghai Inst Technol, Peoples R China.
    Lu, Chun
    Shenyang Aerosp Univ, Peoples R China.
    Xu, Jiayue
    Shanghai Inst Technol, Peoples R China.
    Paul, Biplab
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Flexible n-Type Tungsten Carbide/Polylactic Acid Thermoelectric Composites Fabricated by Additive Manufacturing2018In: Coatings, ISSN 2079-6412, Vol. 8, no 1, article id 25Article in journal (Refereed)
    Abstract [en]

    Flexible n-type tungsten carbide/polylactic acid (WC/PLA) composites were fabricated by additive manufacturing and their thermoelectric properties were investigated. The preparation of an n-type polymer-based thermoelectric composite with good stability in air atmosphere via additive manufacturing holds promise for application in flexible thermoelectric devices. For WC/PLA volume ratios varying from similar to 33% to 60%, the electrical conductivity of the composites increased from 10.6 to 42.2 S/cm, while the Seebeck coefficients were in the range -11 to -12.3 V/K. The thermal conductivities of the composites varied from similar to 0.2 to similar to 0.28 Wamp;lt;boldamp;gt;mamp;lt;/boldamp;gt;-1amp;lt;boldamp;gt;Kamp;lt;/boldamp;gt;-1 at similar to 300 K.

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  • 7.
    Du, Yong
    et al.
    Shanghai Inst Technol, Peoples R China.
    Chen, Jiageng
    Shanghai Inst Technol, Peoples R China.
    Meng, Qiufeng
    Shanghai Inst Technol, Peoples R China.
    Xu, Jiayue
    Shanghai Inst Technol, Peoples R China.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Paul, Biplab
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Flexible Thermoelectric Double-Layer Inorganic/Organic Composites Synthesized by Additive Manufacturing2020In: Advanced Electronic Materials, E-ISSN 2199-160X, Vol. 6, no 8, article id 2000214Article in journal (Refereed)
    Abstract [en]

    This study shows an approach to combine a high electrical conductivity of one composite layer with a high Seebeck coefficient of another composite layer in a double-layer composite, resulting in high thermoelectric power factor. Flexible double-layer-composites, made from Bi2Te3-based-alloy/polylactic acid (BTBA/PLA) composites and Ag/PLA composites, are synthesized by solution additive manufacturing. With the increase in Ag volume-ratio from 26.3% to 41.7% in Ag/PLA layers, the conductivity of the double-layer composites increases from 12 S cm(-1)to 1170 S cm(-1), while the Seebeck coefficient remains approximate to 80 mu V K(-1)at 300 K. With further increase in volume ratio of Ag until 45.6% in Ag/PLA composite layer, the electrical conductivity of the double-layer composites increases to 1710 S cm(-1), however, with a slight decrease of the Seebeck coefficient to 64 mu V K-1. The electrical conductivity and Seebeck coefficient vary only to a limited extent with the temperature. The high Seebeck coefficient is due to scattering of low energy charge carriers across compositionally graded interfaces. A power factor of 875 mu W m(-1) K(-2)is achieved at 360 K for 41.7 vol.% Ag in the Ag/PLA layers. Solution additive manufacturing can directly print this double-layer composite into intricate geometries, making this process is promising for large-scale fabrication of thermoelectric composites.

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  • 8.
    Du, Yong
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Shanghai Inst Technol, Peoples R China.
    Chen, Jiageng
    Shanghai Inst Technol, Peoples R China.
    Meng, Qiufeng
    Shanghai Inst Technol, Peoples R China.
    Xu, Jiayue
    Shanghai Inst Technol, Peoples R China.
    Paul, Biplab
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Flexible ternary carbon black/Bi2Te3 based alloy/polylactic acid thermoelectric composites fabricated by additive manufacturing2020In: Journal of Materiomics, ISSN 2352-8478, E-ISSN 2352-8486, Vol. 6, no 2, p. 293-299Article in journal (Refereed)
    Abstract [en]

    Flexible ternary carbon black/Bi2Te3 based alloy/polylactic acid (CB/BTBA/PLA) composites were fabricated by additive manufacturing and their thermoelectric properties were investigated from 300 K to 360 K. At 300 K, as the mass ratios of BTBAs in the composites increased from 38.5% to 71.4%, both the electrical conductivity and Seebeck coefficient of the composites increased from 5.8 S/cm to 13.3 S/cm, and from 60.2 mV/K to 119.9 mV/K, respectively, and the thermal conductivity slightly increased from 0.15 W m(-1)K(-1) to 0.25 W m(-1)K(-1), as a result, the ZT value of the composites increased from 0.004 to 0.023. As the temperature increased from 300 K to 360 K, the electrical conductivity of all the composites slightly decreased, while the thermal conductivity slowly increased, and a highest ZT value of 0.024 was achieved for the composites with 71.4% BTBAs at 320 K. Unlike traditional sterolithography, fused deposition modeling, selective laser melting, etc., this additive manufacturing process can directly print the solutions which contain inorganic fillers and polymer matrixes into almost any designed intricate geometries of thermoelectric composites, therefore this process has great potential to be used for fabrication of flexible polymer based thermoelectric composites and devices. (C) 2020 The Chinese Ceramic Society. Production and hosting by Elsevier B.V.

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  • 9.
    Du, Yong
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Shanghai Inst Technol, Peoples R China.
    Xu, Jiayue
    Shanghai Inst Technol, Peoples R China.
    Paul, Biplab
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Flexible thermoelectric materials and devices2018In: APPLIED MATERIALS TODAY, ISSN 2352-9407, Vol. 12, p. 366-388Article, review/survey (Refereed)
    Abstract [en]

    Thermoelectric generators (TEGs) can directly convert waste heat into electrical power. In the last few decades, most research on thermoelectrics has focused on inorganic bulk thermoelectric materials and corresponding devices, and their thermoelectric properties have been significantly improved. An emerging topic is flexible devices, where the use of bulk inorganic materials is precluded by their inherent rigidity. The purpose of this paper is to review the research progress on flexible thermoelectric materials and generators, including theoretical principles for TEGs, conducting polymer TE materials, nanocomposites comprised of inorganic nanostructures in polymer matrices and fully inorganic flexible TE materials in nanostructured thin films. Approaches for flexible TEGs and components are reviewed, and remaining challenges discussed. (C) 2018 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

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  • 10.
    Ekström, Erik
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Elsukova, Anna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Grasland, Justine
    IUT BloisUniv Francois Rabelais Tours, France.
    Palisaitis, Justinas
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Ramanath, Ganpati
    Rensselaer Polytech Inst, NY 12180 USA.
    Persson, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Paul, Biplab
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Eriksson, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Le Febvrier, Arnaud
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Epitaxial Growth of CaMnO3-y Films on LaAlO3 (112 over bar 0) by Pulsed Direct Current Reactive Magnetron Sputtering2022In: Physica Status Solidi. Rapid Research Letters, ISSN 1862-6254, E-ISSN 1862-6270, Vol. 16, no 4, article id 2100504Article in journal (Refereed)
    Abstract [en]

    CaMnO3 is a perovskite with attractive magnetic and thermoelectric properties. CaMnO3 films are usually grown by pulsed laser deposition or radio frequency magnetron sputtering from ceramic targets. Herein, epitaxial growth of CaMnO3-y (002) films on a (112 over bar 0)-oriented LaAlO3 substrate using pulsed direct current reactive magnetron sputtering is demonstrated, which is more suitable for industrial scale depositions. The CaMnO3-y shows growth with a small in-plane tilt of <approximate to 0.2 degrees toward the (200) plane of CaMnO3-y and the (1 over bar 104) with respect to the LaAlO3 (112 over bar 0) substrate. X-ray photoelectron spectroscopy of the electronic core levels shows an oxygen deficiency described by CaMnO2.58 that yields a lower Seebeck coefficient and a higher electrical resistivity when compared to stoichiometric CaMnO3. The LaAlO3 (112 over bar 0) substrate promotes tensile-strained growth of single crystals. Scanning transmission electron microscopy and electron energy loss spectroscopy reveal antiphase boundaries composed of Ca on Mn sites along and , forming stacking faults.

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  • 11.
    Ekström, Erik
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hurand, Simon
    Univ Poitiers, France.
    Le Febvrier, Arnaud
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Elsukova, Anna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Persson, Per O A
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Paul, Biplab
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Eriksson, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Sharma, Geetu
    Rensselaer Polytech Inst, NY 12180 USA.
    Voznyy, Oleksandr
    Univ Toronto Scarborough, Canada.
    Sangiovanni, Davide
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Ramanath, Ganpati
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Rensselaer Polytech Inst, NY 12180 USA.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Microstructure control and property switching in stress-free van der Waals epitaxial VO2 films on mica2023In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 229, article id 111864Article in journal (Refereed)
    Abstract [en]

    Realizing stress-free inorganic epitaxial films on weakly bonding substrates is of importance for applications that require film transfer onto surfaces that do not seed epitaxy. Film-substrate bonding is usually weakened by harnessing natural van der Waals layers (e.g., graphene) on substrate surfaces, but this is difficult to achieve in non-layered materials. Here, we demonstrate van der Waals epitaxy of stress-free films of a non-layered material VO2 on mica. The films exhibit out-of-plane 010 texture with three inplane orientations inherited from the crystallographic domains of the substrate. The lattice parameters are invariant with film thickness, indicating weak film-substrate bonding and complete interfacial stress relaxation. The out-of-plane domain size scales monotonically with film thickness, but the in-plane domain size exhibits a minimum, indicating that the nucleation of large in-plane domains supports subsequent island growth. Complementary ab initio investigations suggest that VO2 nucleation and van der Waals epitaxy involves subtle polarization effects around, and the active participation of, surface potassium atoms on the mica surface. The VO2 films show a narrow domain-size-sensitive electrical-conductiv ity-temperature hysteresis. These results offer promise for tuning the properties of stress-free van der Waals epitaxial films of non-layered materials such as VO2 through microstructure control (C) 2023 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

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  • 12.
    Ekström, Erik
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Le Febvrier, Arnaud
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Bourgeois, F.
    Univ Technol Blois, France.
    Lundqvist, Björn
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Palisaitis, Justinas
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Persson, Per O A
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Caballero-Calero, O.
    CEI UAM, Spain.
    Martin-Gonzalez, M. S.
    CEI UAM, Spain.
    Klarbring, Johan
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Simak, Sergey
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Eriksson, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Paul, Biplab
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    The effects of microstructure, Nb content and secondary Ruddlesden-Popper phase on thermoelectric properties in perovskite CaMn1-xNbxO3 (x=0-0.10) thin films2020In: RSC Advances, E-ISSN 2046-2069, RSC ADVANCES, Vol. 10, no 13, p. 7918-7926Article in journal (Refereed)
    Abstract [en]

    CaMn1-xNbxO3 (x = 0, 0.5, 0.6, 0.7 and 0.10) thin films have been grown by a two-step sputtering/annealing method. First, rock-salt-structured (Ca,Mn1-x,Nb-x)O thin films were deposited on 11 & x304;00 sapphire using reactive RF magnetron co-sputtering from elemental targets of Ca, Mn and Nb. The CaMn1-xNbxO3 films were then obtained by thermally induced phase transformation from rock-salt-structured (Ca,Mn1-xNbx)O to orthorhombic during post-deposition annealing at 700 degrees C for 3 h in oxygen flow. The X-ray diffraction patterns of pure CaMnO3 showed mixed orientation, while Nb-containing films were epitaxially grown in [101] out of-plane-direction. Scanning transmission electron microscopy showed a Ruddlesden-Popper (R-P) secondary phase in the films, which results in reduction of the electrical and thermal conductivity of CaMn1-xNbxO3. The electrical resistivity and Seebeck coefficient of the pure CaMnO3 film were measured to 2.7 omega cm and -270 mu V K-1 at room temperature, respectively. The electrical resistivity and Seebeck coefficient were reduced by alloying with Nb and was measured to 0.09 omega cm and -145 mu V K-1 for x = 0.05. Yielding a power factor of 21.5 mu W K-2 m(-1) near room temperature, nearly eight times higher than for pure CaMnO3 (2.8 mu W K-2 m(-1)). The power factors for alloyed samples are low compared to other studies on phase-pure material. This is due to high electrical resistivity originating from the secondary R-P phase. The thermal conductivity of the CaMn1-xNbxO3 films is low for all samples and is the lowest for x = 0.07 and 0.10, determined to 1.6 W m(-1) K-1. The low thermal conductivity is attributed to grain boundary scattering and the secondary R-P phase.

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  • 13.
    Ekström, Erik
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Le Febvrier, Arnaud
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Fournier, Daniele
    Sorbonne Univ, France.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Ene, Vladimir-Lucian
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering. Univ Politehn Bucuresti, Romania.
    Van Nong, Ngo
    Tech Univ Denmark, Denmark.
    Eriksson, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Paul, Biplab
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Formation mechanism and thermoelectric properties of CaMnO3 thin films synthesized by annealing of Ca0.5Mn0.5O films2019In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 54, no 11, p. 8482-8491Article in journal (Refereed)
    Abstract [en]

    A two-step synthesis approach was utilized to grow CaMnO3 on M-, R- and C-plane sapphire substrates. Radio-frequency reactive magnetron sputtering was used to grow rock-salt-structured (Ca, Mn)O followed by a 3-h annealing step at 800 degrees C in oxygen flow to form the distorted perovskite phase CaMnO3. The effect of temperature in the post-annealing step was investigated using x-ray diffraction. The phase transformation to CaMnO3 started at 450 degrees C and was completed at 550 degrees C. Films grown on R- and C-plane sapphire showed similar structure with a mixed orientation, whereas the film grown on M-plane sapphire was epitaxially grown with an out-of-plane orientation in the [202] direction. The thermoelectric characterization showed that the film grown on M-plane sapphire has about 3.5 times lower resistivity compared to the other films with a resistivity of 0.077cm at 500 degrees C. The difference in resistivity is a result from difference in crystal structure, single orientation for M-plane sapphire compared to mixed for R- and C-plane sapphire. The highest absolute Seebeck coefficient value is -350 mu VK-1 for all films and is decreasing with temperature.

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  • 14.
    Magnusson, Roger
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Paul, Biplab
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Greczynski, Grzegorz
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Jonsson, Bo
    School of Engineering, Department of Built Environment and Energy Technology, Linnæus University, Växjö, Sweden.
    Ali, Sharafat
    School of Engineering, Department of Built Environment and Energy Technology, Linnæus University, Växjö, Sweden.
    Preparation and tunable optical properties of amorphous AlSiO thin films2021In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 187, article id 110074Article in journal (Refereed)
    Abstract [en]

    Thin films in the aluminosilicate (AlSiO) system containing up to 31 at. % Al and 23 at. % Si were prepared by reactive RF magnetron co-sputtering in order to investigate the dependence of film formation and optical properties on substrate temperature and Si and Al contents. The obtained films were amorphous with smooth microstructure. The growth rate at different substrate temperatures ranged from 1.2 to 3.3 nm/min and increase with increasing the Si target power. The roughness decreases and thickness increases with increasing Si content. The thickness of the films grown at a deposition temperature of 100 °C is found to be higher than the films deposited at 300 and 500 °C. The AlSiO-coated glasses have a higher transmission in the visible region than the uncoated glass. The spectroscopic ellipsometry analysis reveals that the refractive index value decreased with decreasing the Al content, having extinction coefficient values of zero in the measured spectral region and band gap values ≥ 3.4 eV. The obtained thin films have over 90% transmittance in the visible range and no systematic variation of transmittance was observed with substrate temperature. The results suggest that glass substrate coated with AlSiO thin films have improved optical properties.

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  • 15.
    Paul, Biplab
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Björk, Emma M.
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
    Kumar, Aparabal
    Materials Science Centre, Indian Institute of Technology, Kharagpur 721302, India.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Nanoporous Ca3Co4O9 Thin Films for Transferable Thermoelectrics2018In: ACS Applied Energy Materials, E-ISSN 2574-0962, Vol. 1, no 5, p. 2261-2268Article in journal (Refereed)
    Abstract [en]

    The development of high-performance and transferable thin-film thermoelectric materials is important for low-power applications, e.g., to power wearable electronics, and for on-chip cooling. Nanoporous films offer an opportunity to improve thermoelectric performance by selectively scattering phonons without affecting electronic transport. Here, we report the growth of nanoporous Ca3Co4O9 thin films by a sequential sputtering-annealing method. Ca3Co4O9 is promising for its high Seebeck coefficient and good electrical conductivity and important for its nontoxicity, low cost, and abundance of its constituent raw materials. To grow nanoporous films, multilayered CaO/CoO films were deposited on sapphire and mica substrates by rf-magnetron reactive sputtering from elemental Ca and Co targets, followed by annealing at 700 C to form the final phase of Ca3Co4O9. This phase transformation is accompanied by a volume contraction causing formation of nanopores in the film. The thermoelectric propoperties of the nanoporous Ca3Co4O9 films can be altered by controlling the porosity. The lowest electrical resistivity is ~7 mO cm, yielding a power factor of 2.32 × 10-4 Wm-1K-2 near room temperature. Furthermore, the films are transferable from the primary mica substrates to other arbitrary polymer platforms by simple dry transfer, which opens an opportunity of low-temperature use these materials.

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  • 16.
    Paul, Biplab
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Khranovskyy, Volodymyr
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Donor-doped ZnO thin films on mica for fully-inorganic flexible thermoelectrics2019In: Materials Research Letters, E-ISSN 2166-3831, Vol. 7, no 6, p. 239-243Article in journal (Refereed)
    Abstract [en]

    The development of fully-inorganic thin flexible materials is important for flexible thermoelectric applications in a wide temperature range, such as harvesting power from hot curved surfaces (e.g. hot pipes). Here, we investigate the thermoelectric properties of a series of ZnO:Ga,Al thin films with varying dopant concentration deposited on flexible mica substrate by atmospheric pressure metalorganic chemical vapor deposition. The films are bendable, while sustaining the high power factor, above 1 x 10(-4)Wm(-1)K(-2) for singly doped Zn0.99Ga0.01O film in a wide temperature range, from room temperature to 400 degrees C. IMPACT STATEMENTFor the first time we demonstrate here that ZnO-film-on-mica can be a promising n-type candidate for fully-inorganic flexible thermoelectrics, especially, for applications at elevated temperatures [GRAPHICS]

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  • 17.
    Paul, Biplab
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Growth of CaxCoO2 Thin Films by A Two-Stage Phase Transformation from CaO-CoO Thin Films Deposited by Rf-Magnetron Reactive Cosputtering2019In: Nanomaterials, E-ISSN 2079-4991, Vol. 9, no 3, article id 443Article in journal (Refereed)
    Abstract [en]

    The layered cobaltates A(x)CoO(2) (A: alkali metals and alkaline earth metals) are of interest in the area of energy harvesting and electronic applications, due to their good electronic and thermoelectric properties. However, their future widespread applicability depends on the simplicity and cost of the growth technique. Here, we have investigated the sputtering/annealing technique for the growth of CaxCoO2 (x = 0.33) thin films. In this approach, CaO-CoO film is first deposited by rf-magnetron reactive cosputtering from metallic targets of Ca and Co. Second, the as-deposited film is reactively annealed under O-2 gas flow to form the final phase of CaxCoO2. The advantage of the present technique is that, unlike conventional sputtering from oxide targets, the sputtering is done from the metallic targets of Ca and Co; thus, the deposition rate is high. Furthermore, the composition of the film is controllable by controlling the power at the targets.

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  • 18.
    Paul, Biplab
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Nanostructural Tailoring to Induce Flexibility in Thermoelectric Ca3Co4O9 Thin Films2017In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 9, no 30, p. 25308-25316Article in journal (Refereed)
    Abstract [en]

    Because of their inherent rigidity and brittleness, inorganic materials have seen limited use in flexible thermoelectric applications. On the other hand, for high output power density and stability, the use of inorganic materials is required. Here, we demonstrate a concept of fully inorganic flexible thermoelectric thin films with Ca3Co4O9-on-mica. Ca3Co4O9 is promising not only because of its high Seebeck coefficient and good electrical conductivity but also because of the abundance, low cost, and nontoxicity of its constituent raw materials. We show a promising nanostructural tailoring approach to induce flexibility in inorganic thin-film materials, achieving flexibility in nanostructured Ca3Co4O9 thin films. The films were grown by thermally induced phase transformation from CaO-CoO thin films deposited by reactive rf-magnetron cosputtering from metallic targets of Ca and Co to the final phase of Ca3Co4O9 on a mica substrate. The pattern of nanostructural evolution during the solid-state phase transformation is determined by the surface energy and strain energy contributions, whereas different distributions of CaO and CoO phases in the as-deposited films promote different nanostructuring during the phase transformation. Another interesting fact is that the Ca3Co4O9 film is transferable onto an arbitrary flexible platform from the parent mica substrate by etch-free dry transfer. The highest thermoelectric power factor obtained is above 1 x 10(-4) W m(-1) K-2 in a wide temperature range, thus showing low-temperature applicability of this class of materials.

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  • 19.
    Paul, Biplab
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Schroeder, Jeremy Leroy
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Kerdsongpanya, Sit
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    van Nong, Ngo
    Risö-DTU, Denmark.
    Schell, Norbert
    Helmholtz-Zentrum Geestacht, Germany.
    Ostach, Daniel
    Helmholtz-Zentrum Geestacht, Germany.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Mechanism of Formation of the Thermoelectric Layered Cobaltate Ca3Co4O9 by Annealing of CaO-CoO Thin Films2015In: Advanced Electronic Materials, E-ISSN 2199-160X, Vol. 1, no 3, article id 1400022Article in journal (Refereed)
    Abstract [en]

    The layered cobaltate Ca3Co4O9 is of interest for energy-harvesting and heat-conversion applications because of its good thermoelectric properties and the fact that the raw materials Ca and Co are nontoxic, abundantly available, and inexpensive. While single-crystalline Ca3Co4O9 exhibits high Seebeck coefficient and low resistivity, its widespread use is hampered by the fact that single crystals are too small and expensive. A promising alternative approach is the growth of highly textured and/or epitaxial Ca3Co4O9 thin films with correspondingly anisotropic properties. Here, we present a two-step sputtering/annealing method for the formation of highly textured virtually phase-pure Ca3Co4O9 thin films by reactive cosputtering from Ca and Co targets followed by an annealing process at 730 °C under O2-gas flow. The thermally induced phase transformation mechanism is investigated by in situ time-resolved annealing experiments using synchrotron-based 2D X-ray diffraction (XRD) as well as ex situ annealing experiments and standard lab-based XRD. By tuning the proportion of initial CaO and CoO phases during film deposition, the method enables synthesis of Ca3Co4O9 thin films as well as CaxCoO2. With this method, we demonstrate production of epitaxial Ca3Co4O9 thin films with in-plane electrical resistivity of 6.44 mΩ cm and a Seebeck coefficient of 118 μV K−1 at 300 K.

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  • 20.
    Paul, Biplab
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Zhang, Yun
    Rensselaer Polytech Inst, NY 12180 USA.
    Zhu, Wenkai
    Rensselaer Polytech Inst, NY 12180 USA.
    Xin, Binbin
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Ramanath, Ganpati
    Rensselaer Polytech Inst, NY 12180 USA.
    Borca-Tasciuc, Theodorian
    Rensselaer Polytech Inst, NY 12180 USA.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Effect of disordered nanoporosity on electrical and thermal properties of layered Ca3Co4O9 films2022In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 120, no 6, article id 061904Article in journal (Refereed)
    Abstract [en]

    Independently controlling electronic and thermal transport in solids is a challenge, because these properties are coupled. Here, we show that disordered nanoporosity in Ca3Co4O9 thin films can decrease the thermal conductivity without significantly hampering electronic transport. Scanning thermal microscopy was used to determine the out-of-plane thermal conductivity and estimate the in-plane values. Nanoporous Ca3Co4O9 films exhibit a thermal conductivity of 0.82 W m(-1) K-1, which is nearly twofold lower than that obtained from nonporous Ca3Co4O9 films. Nanoporous Ca3Co4O9 exhibit a room-temperature electrical resistivity of 4 m omega cm, which is comparable to polycrystalline Ca3Co4O9 and twice that reported for single-crystal Ca3Co4O9. Our results suggest that controlling nanoporosity and their degree of disorder can offer a means of decoupling electrical and thermal properties in materials.

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  • 21.
    Rawat, Pankaj K.
    et al.
    Indian Institute Technology, India; Science and Engn Research Board, India.
    Paul, Biplab
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Simple design for Seebeck measurement of bulk sample by 2-probe method concurrently with electrical resistivity by 4-probe method in the temperature range 300-1000 K2016In: Measurement, ISSN 0263-2241, E-ISSN 1873-412X, Vol. 91, p. 613-619Article in journal (Refereed)
    Abstract [en]

    The 4-probe method has so far been the most popular method for concurrent measurement of Seebeck coefficient and electrical resistivity of bulk samples. However, for Seebeck measurement with higher accuracy, the 2-probe method is becoming preferred over 4-probe method. The problem with the previous apparatus designs is that they do not allow 2-probe arrangement for Seebeck measurement simultaneously with linear 4-probe arrangement for electrical resistivity measurement. So, the challenge is find a design where two different probe arrangements become possible at the same time in a single measurement run. Here, we report design and fabrication of an apparatus that allows Seebeck measurement by 2-probe method concurrently with electrical resistivity by 4-probe method of bar and disc samples in the temperature range from 300 to 1000 K. The uniqueness of the present design is that it does not require heating the entire sample chamber for temperature dependent measurements. This is because a small cylindrical furnace inside the sample chamber is used to control the sample background temperature. This internal furnace arrangement results in readily achievable set temperature with desired uniformity. Thus, it allows faster thermoelectric evaluation of samples. The design includes several preventive steps to negate the effect of off-axial heat flows on the measurement accuracy. The measurement error in Seebeck coefficient and electrical resistivity of PbTe sample is estimated to be smaller than 5%. (C) 2016 Elsevier Ltd. All rights reserved.

  • 22.
    Sinha, Tridib Kumar
    et al.
    Indian Inst Technol, India; Gyeongsang Natl Univ, South Korea.
    Lee, Jinho
    Gyeongsang Natl Univ, South Korea.
    Kim, Jin Kuk
    Gyeongsang Natl Univ, South Korea.
    Ray, Samit K.
    Indian Inst Technol, India; SN Bose Natl Ctr Basic Sci, India.
    Paul, Biplab
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Rapid growth of fully-inorganic flexible CaxCoO2 thin films from a ligand free aqueous precursor ink for thermoelectric applications2019In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 55, no 54, p. 7784-7787Article in journal (Refereed)
    Abstract [en]

    We demonstrate a ligand-free green chemical method for the rapid growth of nanoporous Ca0.35CoO2 thin films on sapphire and mica substrates from a water-based precursor ink, formulated by dissolving the precursor solid, composed of in situ prepared Ca2+-DMF and Co2+-DMF complexes. Mica serves as the flexible substrate as well as the sacrificial layer for the film transfer. Despite the presence of nanopores, the power factor of the flexible film Ca0.35CoO2-on-mica is above 0.50 x 10(-4) W m(-1) K-2 at around room temperature. The present technique is simple and cost-effective.

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  • 23.
    Xin, Binbin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Ekström, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Shih, Yueh-Ting
    Rensselaer Polytech Inst, NY 12180 USA.
    Huang, Liping
    Rensselaer Polytech Inst, NY 12180 USA.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Elsukova, Anna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Zhang, Yun
    Rensselaer Polytech Inst, NY 12180 USA.
    Zhu, Wenkai
    Rensselaer Polytech Inst, NY 12180 USA.
    Borca-Tasciuc, Theodorian
    Rensselaer Polytech Inst, NY 12180 USA.
    Ramanath, Ganpati
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Rensselaer Polytech Inst, NY 12180 USA.
    Le Febvrier, Arnaud
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Paul, Biplab
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Engineering thermoelectric and mechanical properties by nanoporosity in calcium cobaltate films from reactions of Ca(OH)(2)/Co3O4 multilayers2022In: Nanoscale Advances, E-ISSN 2516-0230, Vol. 4, no 16, p. 3353-3361Article in journal (Refereed)
    Abstract [en]

    Controlling nanoporosity to favorably alter multiple properties in layered crystalline inorganic thin films is a challenge. Here, we demonstrate that the thermoelectric and mechanical properties of Ca3Co4O9 films can be engineered through nanoporosity control by annealing multiple Ca(OH)(2)/Co3O4 reactant bilayers with characteristic bilayer thicknesses (b(t)). Our results show that doubling b(t), e.g., from 12 to 26 nm, more than triples the average pore size from similar to 120 nm to similar to 400 nm and increases the pore fraction from 3% to 17.1%. The higher porosity film exhibits not only a 50% higher electrical conductivity of sigma similar to 90 S cm(-1) and a high Seebeck coefficient of alpha similar to 135 mu V K-1, but also a thermal conductivity as low as kappa similar to 0.87 W m(-1) K-1. The nanoporous Ca3Co4O9 films exhibit greater mechanical compliance and resilience to bending than the bulk. These results indicate that annealing reactant multilayers with controlled thicknesses is an attractive way to engineer nanoporosity and realize mechanically flexible oxide-based thermoelectric materials.

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  • 24.
    Xin, Binbin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Le Febvrier, Arnaud
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Paul, Biplab
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Platit AG, Switzerland.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Synthesis of textured discontinuous-nanoisland Ca3Co4O9 thin films2022In: Nanoscale Advances, E-ISSN 2516-0230, Vol. 4, p. 3318-3322Article in journal (Refereed)
    Abstract [en]

    Controllable engineering of the nanoporosity in layered Ca3Co4O9 remains a challenge. Here, we show the synthesis of discontinuous films with islands of highly textured Ca3Co4O9, effectively constituting distributed nanoparticles with controlled porosity and morphology. These discontinuously dispersed textured Ca3Co4O9 nanoparticles may be a candidate for hybrid thermoelectrics.

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  • 25.
    Xin, Binbin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Le Febvrier, Arnaud
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Shu, Rui
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Elsukova, Anna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Venkataramani, Venkat
    Rensselaer Polytech Inst, NY 12180 USA.
    Shi, Yunfeng
    Rensselaer Polytech Inst, NY 12180 USA.
    Ramanath, Ganpati
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Rensselaer Polytech Inst, NY 12180 USA.
    Paul, Biplab
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Engineering Faceted Nanoporosity by Reactions in Thin-Film Oxide Multilayers in Crystallographically Layered Calcium Cobaltate for Thermoelectrics2021In: ACS Applied Nano Materials, E-ISSN 2574-0970, Vol. 4, no 9, p. 9904-9911Article in journal (Refereed)
    Abstract [en]

    Introducing porosity is attractive for tailoring electronic, thermal, and mechanical properties of inorganic materials. Nanoporosity is typically either inherent in crystallographic channels in the structure or obtained by external templating during synthesis and sintering. However, controllably engineering porosity in materials with laminated crystal structures without channels remains a challenge. Here, we demonstrate the realization of faceted and oriented nanopores in textured Ca3Co4O9-a laminated ceramic with a misfit-layered structure of importance for thermoelectric applications-from chemical reactions in CaO/Co3O4 multilayers. We show that CaO conversion to Ca(OH)(2) and the cobalt oxide stoichiometry are key determinants of nanoporosity. Adjusting the unreacted CaO fraction alters the nanopore size and fraction and the thermoelectric properties of Ca3Co4O9. The preferred orientation of Ca3Co4O9 is underpinned by the texture of the reactant multilayers and reactant-product crystallographic relationships and density difference. Oriented pore formation is attributed to basal plane removal driven by local densification of textured Ca3Co4O9 nuclei through growth and impingement. These findings point to possibilities for controllably engineering nanoporosity and properties in a variety of inorganic materials with laminated crystal structures.

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  • 26.
    Xin, Binbin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Le Febvrier, Arnaud
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Wang, Lei
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Solin, Niclas
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Paul, Biplab
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Growth and optical properties of CaxCoO2 thin films2021In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 210, article id 110033Article in journal (Refereed)
    Abstract [en]

    The layered cobaltates A(x)CoO(2) (A = Li, Na, Ca, Ba, Sr) are of interest for energy applications such as thermoelectrics and batteries. However, it is challenging to obtain these phases in pure from as thin films. Here, phase-pure CaxCoO2 (x similar to 0.5) thin films were obtained by annealing of Ca(OH)(2)/Co3O4 multilayers made by moisture treatment of sputter-deposited CaO/Co3O4 multilayer films. The pure CaxCoO2 thin films exhibit an average optical transmittance of approximately 36% in the visible region and greater than 70% in the near-infrared (NIR) region. In addition, the electrical conductivity can be increased by incorporating a secondary Ca3Co4O9 phase into the CaxCoO2 thin film without large changes in optical properties and Seebeck coefficient. (C) 2021 The Authors. Published by Elsevier Ltd.

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  • 27.
    Xin, Binbin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Paul, Biplab
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Platit AG, Switzerland.
    Le Febvrier, Arnaud
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Thin-film thermocouples of Ni-joined thermoelectric Ca3Co4O92023In: Materials Science in Semiconductor Processing, ISSN 1369-8001, E-ISSN 1873-4081, Vol. 156, article id 107300Article in journal (Refereed)
    Abstract [en]

    Thin-film Ni-Ca3Co4O9 and Ni-Mo thermocouples were prepared by stepwise magnetron-sputtering/annealing synthesis using masks. Compared with Ni-Mo thin film thermocouples, Ni-Ca3Co4O9 thin film thermocouples have higher output voltage due to large positive Seebeck voltage (153 mu V/K for single thermocouple and 912 mu V/ K for 6-series thermocouple). The maximum output voltage from the thermocouple is 70 mV was obtained for a hot-end temperature of 105 degrees C for Ni-Ca3Co4O9 for a 6-series thermocouple. The stability of Ca3Co4O9 films and the ability to make free-standing films, together with the high Seebeck coefficient, show that these thin-film oxides can be used as p-type leg in thermocouples, with implications for use in free-standing and flexible thermoelectric devices.

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  • 28.
    Xin, Binbin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Wang, Lei
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Le Febvrier, Arnaud
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Elsukova, Anna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Paul, Biplab
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Solin, Niclas
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Mechanically Flexible Thermoelectric Hybrid Thin Films by Introduction of PEDOT:PSS in Nanoporous Ca3Co4O92022In: ACS Omega, E-ISSN 2470-1343, Vol. 7, no 27, p. 23988-23994Article in journal (Refereed)
    Abstract [en]

    Nanoporous Ca3Co4O9 exhibits high thermoelectric properties and low thermal conductivity and can be made mechanically flexible by nanostructural design. To improve the mechanical flexibility with retained thermoelectric properties near room temperature, however, it is desirable to incorporate an organic filler in this nanoporous inorganic matrix material. Here, double-layer nanoporous Ca3Co4O9/PEDOT:PSS thin films were synthesized by spin-coating PEDOT:PSS into the nanopores. The obtained hybrid films exhibit high Seebeck coefficient (~+130 mu V/K) and thermoelectric power factor (0.75 mu W cm(-1) K-2) at room temperature with no deterioration in electrical properties after cyclic bending tests (98% preservation of electrical conductivity after 1000 cycles bending to a bending radius of 3 mm). Compared with the nanoporous Ca3Co4O9 thin film, the mechanical flexibility of the hybrid film can be effectively improved after hybrid with PEDOT:PSS with only a slight decrease of the thermoelectric properties.

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