<i>In situ</i> growth of c-axis-oriented Ca3Co4O9 thin films on Si (100)

Hu, Yufeng; D., W.; Sutter, Eli; Li, Qiang

doi:10.1063/1.1868873

Cited by 94 publications

(79 citation statements)

References 11 publications

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“…This is very different from the previous TEM analysis of Ca 3 Co 4 O 9 thin films grown on single crystal sapphire (001)-oriented, glass, or (100)-silicon, where the presence of both secondary phases and low-crystallinity structures at the interface were reported. [24][25][26] In our present study, the absence of an amorphous layer close to the interface clearly confirmed the good texture and the epitaxial nature of the Ca 3 Co 4 O 9 thin film with respect to each grain and will be discussed hereafter with respect to the thermoelectric properties. It should be clear that the Ca 3 Co 4 O 9 epitaxial film growth was achieved without the classical substrate-induced epitaxy arising from interactions with low-index surfaces of single-crystal substrates, which is very different from the previous reports.…”

supporting

confidence: 56%

High-throughput synthesis of thermoelectric Ca3Co4O9 films

Dhanapal

Lebedev

Hébert

et al. 2013

Applied Physics Letters

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Properties of complex oxide thin films can be tuned over a range of values as a function of mismatch, composition, orientation, and structure. Here, we report a strategy for growing structured epitaxial thermoelectric thin films leading to improved Seebeck coefficient. Instead of using single-crystal sapphire substrates to support epitaxial growth, Ca3Co4O9 films are deposited, using the Pulsed Laser Deposition technique, onto Al2O3 polycrystalline substrates textured by spark plasma sintering. The structural quality of the 2000 Å thin film was investigated by transmission electron microscopy, while the crystallographic orientation of the grains and the epitaxial relationships were determined by electron backscatter diffraction. The use of a polycrystalline ceramic template leads to structured films that are in good local epitaxial registry. The Seebeck coefficient is about 170 μV/K at 300 K, a typical value of misfit material with low carrier density. This high-throughput process, called combinatorial substrate epitaxy, appears to facilitate the rational tuning of functional oxide films, opening a route to the epitaxial synthesis of high quality complex oxides.

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supporting

confidence: 56%

High-throughput synthesis of thermoelectric Ca3Co4O9 films

Dhanapal

Lebedev

Hébert

et al. 2013

Applied Physics Letters

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“…4͒ and approaches the lattice constant of the CCO349 films prepared by PLD ͑10.70 Å͒, indicating that the derived CCO349 films are in-plane tensile strained. 5,7 A similar shortening of the c-axis lattice constant for all the films suggests that there have been the same inplane tensile stress for all derived films, which can be attributed to the dewetting and will be discussed below.…”

Section: Methodsmentioning

confidence: 85%

“…[1][2][3] The CCO349 is built up by stacking along the c-axis of triple rock salt-type layer Ca 2 CoO 3 and single CdI 2 -type CoO 2 layers, which both have monoclinic symmetry with identical a, c, and ␤, but different b parameters ͑for the Ca 2 CoO 3 layer, a = 4.8376 Å, c = 10.833 Å, ␤ = 98.06°, and b 1 = 4.5565 Å, while for the CoO 2 layer, b 2 = 2.8189 Å͒. 4 As for the fabrication of CCO349 films, which can be used in various applications 5 such as thermochemistry-on-achip, biothermoelectric chips, active cooling for microelectronic processors, and localized cooling/heating at points of interest, the commonly used method is pulsed laser deposition ͑PLD͒, [6][7][8] and there have few reports about the chemical solution deposition ͑CSD͒ route, 9 which is a simple, low-cost method for large-area films. Moreover, in the processes of preparing films, the interfacial strain in the films is a key parameter controlling many physical properties, which has stimulated considerable efforts towards understanding the relaxation mechanisms.…”

Section: Introductionmentioning

confidence: 99%

Growth of Ca3Co4O9 films: Simple chemical solution deposition and stress induced spontaneous dewetting

Zhu

Sun

Lei

et al. 2007

Journal of Applied Physics

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Chemical solution deposition as a simple method for preparation of oxide films is used to fabricate misfit structured Ca 3 Co 4 O 9 thermoelectric films using cheap precursors, Ca and Co acetates, which opens up a simple route to fabricate large-area Co-based oxide thermoelectric films. The results show that when the annealing temperature is higher than 800°C crystallized Ca 3 Co 4 O 9 films can be obtained on single-crystal LaAlO 3 substrates, whereas the Ca 3 Co 4 O 9 films are amorphous for lower annealing temperatures. Experimental evidence shows that the amorphous Ca 3 Co 4 O 9 films behave like semiconductors with enhanced resistivity and Seebeck coefficient within the measured temperature range. The magnetoresistance is positive indicating the absence of long-range order of the Co-ion spins. For the crystallized Ca 3 Co 4 O 9 films, it can be seen that the thinner films show the characteristics of spontaneous dewetting induced by the stress, which suggests that it is possible to prepare nanostructured Ca 3 Co 4 O 9 films through tailoring the film thickness and the lattice mismatch; whereas, for the thicker films the temperature dependence of the resistivity and the Seebeck coefficient shows that it is possible to prepare excellent Ca 3 Co 4 O 9 thermoelectric films using chemical solution deposition route, which will broaden the range of preparation methods for misfit structured Co-based thermoelectric films.

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“…The electrical resistivity (Figure 7a) of the Ca:Co=0.72 film is lower than that of the Ca-rich and Co-rich samples throughout the measured temperature range, owing to its phase purity. The room temperature electrical resistivity of the phase pure sample (6.44 mΩcm) is comparable to most Ca 3 Co 4 O 9 thin films grown by different techniques, [8][9][10][11][12][13][14][15][16][17][18][19][20][21] but somewhat higher than the lowest reported electrical resistivity value for Ca 3 Co 4 O 9 thin films deposited on glass substrates (~4 mΩcm). [ 28 ] The electrical resistivity of the Ca-rich and Co-rich samples increases with increasing deviation of the Ca:Co ratio from the stoichiometric limit, which is attributed to enhanced scattering of charge carriers by the grains of impurity oxide phases.…”

Section: Thermoelectric Propertiesmentioning

confidence: 91%

Mechanism of Formation of the Thermoelectric Layered Cobaltate Ca₃Co₄O₉ by Annealing of CaO–CoO Thin Films

Paul

Schroeder

Kerdsongpanya

et al. 2015

Adv Elect Materials

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The layered cobaltate Ca 3 Co 4 O 9 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 non-toxic, abundantly available, and inexpensive. While single-crystalline Ca 3 Co 4 O 9 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 Ca 3 Co 4 O 9 thin films with correspondingly anisotropic properties. Here, we present a two-step sputtering/annealing method for the formation of highly textured virtually phase-pure Ca 3 Co 4 O 9 thin films by reactive co-sputtering from Ca and Co targets followed by an annealing process at 730 °C under O 2 -gas flow. The thermally induced phase transformation mechanism was investigated by in-situ time-resolved annealing experiments using synchrotron-based 2D x-ray diffraction as well as ex-situ annealing experiments and standard lab-based x-ray diffraction. By tuning the proportion of initial CaO and CoO phases during film deposition, the method enables synthesis of Ca 3 Co 4 O 9 thin films as well as Ca x CoO 2 . With this method, we demonstrate production of epitaxial Ca 3 Co 4 O 9 thin films with in-plane electrical resistivity of 6.44 mΩcm and a Seebeck coefficient of 118 µVK -1 at 300 K.3

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In situ growth of c-axis-oriented Ca3Co4O9 thin films on Si (100)

Abstract: Enhanced high temperature thermoelectric properties of Bi-doped c -axis oriented Ca 3 Co 4 O 9 thin films by pulsed laser deposition

Cited by 94 publications

References 11 publications

High-throughput synthesis of thermoelectric Ca3Co4O9 films

High-throughput synthesis of thermoelectric Ca3Co4O9 films

Growth of Ca3Co4O9 films: Simple chemical solution deposition and stress induced spontaneous dewetting

Mechanism of Formation of the Thermoelectric Layered Cobaltate Ca₃Co₄O₉ by Annealing of CaO–CoO Thin Films

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In situ growth of c-axis-oriented Ca3Co4O9 thin films on Si (100)

Abstract: Enhanced high temperature thermoelectric properties of Bi-doped c -axis oriented Ca 3 Co 4 O 9 thin films by pulsed laser deposition

Cited by 94 publications

References 11 publications

High-throughput synthesis of thermoelectric Ca3Co4O9 films

High-throughput synthesis of thermoelectric Ca3Co4O9 films

Growth of Ca3Co4O9 films: Simple chemical solution deposition and stress induced spontaneous dewetting

Mechanism of Formation of the Thermoelectric Layered Cobaltate Ca3Co4O9 by Annealing of CaO–CoO Thin Films

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Mechanism of Formation of the Thermoelectric Layered Cobaltate Ca₃Co₄O₉ by Annealing of CaO–CoO Thin Films