Layered cobalt oxides based on the hexagonal CoO2 layer, e.g., NaxCoO2 and [CoCa3O3]0.62CoO2 (or “Ca3Co4O9”), are promising thermoelectric materials. Here, the authors investigate the atomic layer deposition (ALD) of these materials in a thin-film form; this is not trivial, in particular, for the former compound, as both Na and Co are little challenged as components of ALD thin films. The authors employ diketonate precursors for all the metal constituents and ozone as the source of oxygen. In both cases, a postdeposition heat-treatment in O2 is applied to get crystalline coatings; the processes are found amazingly robust in terms of metal precursor pulsing ratios. A striking difference between the two processes is the resultant morphology: while the Ca3Co4O9 films grow highly homogeneous and smooth, the NaxCoO2 coatings exhibit a rather unique reproducible 10–20 μm scale channel-like island structure for all x values investigated. Finally, the authors characterized their ALD Ca3Co4O9 films for their chemical, structural, and physical property details not previously reported.
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Research Article|
April 28 2020
Atomic layer deposition of thermoelectric layered cobalt oxides
Special Collection:
Atomic Layer Deposition (ALD)
Dirk J. Hagen
;
Dirk J. Hagen
Department of Chemistry and Materials Science, Aalto University
, 02150 Espoo, Finland
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Maarit Karppinen
Maarit Karppinen
a)
Department of Chemistry and Materials Science, Aalto University
, 02150 Espoo, Finland
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a)
Electronic mail: maarit.karppinen@aalto.fi
Note: This paper is part of the 2021 Special Topic Collection on Atomic Layer Deposition (ALD).
J. Vac. Sci. Technol. A 38, 032412 (2020)
Article history
Received:
March 02 2020
Accepted:
April 06 2020
Citation
Dirk J. Hagen, Maarit Karppinen; Atomic layer deposition of thermoelectric layered cobalt oxides. J. Vac. Sci. Technol. A 1 May 2020; 38 (3): 032412. https://doi.org/10.1116/6.0000166
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