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Microstructure/dielectric property relationship of low temperature synthesised (Na,K)NbOx thin films
Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics.ORCID iD: 0000-0002-1744-7322
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2004 (English)In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 262, no 1-4, p. 322-326Article in journal (Refereed) Published
Abstract [en]

Thin films of (Na,K)NbOx (NKN) were grown by reactive RF magnetron sputtering on polycrystalline Pt80Ir20 substrates, at relatively low growth temperatures between 300°C and 450°C. The results show that the electrical performance and the microstructure of the films are a strong function of the substrate temperature. X-ray diffraction of films grown up to 400°C revealed the formation of only one crystalline NKN-phase with a preferred (0 0 2)-orientation. However, a mixed orientation together with a secondary, paraelectric potassium niobate phase, were observed for NKN films deposited at 450°C. The differences in the microstructure explains the variations in the dielectric constants and losses: The single phase NKN films displayed a dielectric constant and a dielectric loss of 506 and 0.011, respectively, while the films with mixed phases exhibited values of 475 and 0.022, respectively. The possibility of fabricating NKN films with relatively high dielectric properties at low growth temperatures, as demonstrated here, is of high technological importance.

Place, publisher, year, edition, pages
2004. Vol. 262, no 1-4, p. 322-326
Keywords [en]
A1. Characterization, A3. Physical vapor deposition processes, B1. Niobates, B2. Dielectric materials
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-45820DOI: 10.1016/j.jcrysgro.2003.10.035ISI: 000189098700050OAI: oai:DiVA.org:liu-45820DiVA, id: diva2:266716
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2021-09-10
In thesis
1. Colloidal Synthesis and Characterisation of (a) Na0.5K0.5NbO3 Thin Films; and (b) Functionalised Gd2O3 Nanocrystals
Open this publication in new window or tab >>Colloidal Synthesis and Characterisation of (a) Na0.5K0.5NbO3 Thin Films; and (b) Functionalised Gd2O3 Nanocrystals
2004 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

(a) Thin films of the perovskite structured Na0.5K0.5NbO3 (NKN) have been synthesised with several different sol-gel methods. Only one method gave pure NKN phase while the other methods gave extra peaks in the x-ray diffraction patterns, indicating that other, unidentified, phases were present. Scanning electron microscopy revealed grain sizes ranging from about 50 to 300 nm. The films prepared by chemical methods are compared with sputtered thin films.

(b) Nanocrystals of Gd2O3 have been prepared by various methods, using e.g. trioctylphosphine oxide (TOPO), diethylene glycol (DEG). The crystalline particles were of sizes 5 to 15 nm. Onto the surface of the particles, made with DEG, different carboxylic acids e.g. oleic acid or citric acid etc, were adsorbed. From IR measurements the bonding to the surface is recognised as chemisorbed via the carboxylate group in a bidentate or bridging fashion, with preference for the bridging coordination. The organic acid-particle complexes were characterised by XRPD, TEM, FTIR, Raman and XPS.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2004. p. 71
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1115
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-54128 (URN)LiU-TEK-LIC-2004:44 (Local ID)91-8529-531-0 (ISBN)LiU-TEK-LIC-2004:44 (Archive number)LiU-TEK-LIC-2004:44 (OAI)
Presentation
(English)
Opponent
Supervisors
Available from: 2010-02-25 Created: 2010-02-24 Last updated: 2023-02-24Bibliographically approved
2. Preparation of Functional Oxide Perovskites: A Study on the Growth-Microstructure-Property Relationships of(N a,K)NbOx Thin Films
Open this publication in new window or tab >>Preparation of Functional Oxide Perovskites: A Study on the Growth-Microstructure-Property Relationships of(N a,K)NbOx Thin Films
2003 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Sodium-potassium niobate is a material with ferroelectric and piezoelectric properties that has been known since 1954. Recently, perovskite structured ferroelectric thin films have gained a lot of attention due to their wide area of potential applications, including non-volatile memories, infrared sensors, optical switches, and ultrasonic transducers. Perovskite-structured thin films of (Na,K)NbOx (hereafter NKN) show high piezoelectric and dielectric constants, low losses (tan δ), and tunable properties, which makes them particularly interesting for device applications.

The possibility of fabricating high electrical performance NKN films at low growth temperatures is of high technological importance. In this thesis, we investigated the feasibility of using reactive rf magnetron sputtering to obtain high-quality dielectric NKN films at low growth temperatures.

Specifically, the aims of this work were (1) to obtain a better understanding of the relation between the process conditions and the resulting chemical compositions and microstructures of NKN films, (2) to investigate how their physical properties depend on the composition and the microstructure, and (3) to optimize the synthesis for obtaining films with improved electrical and mechanical properties.

Our results can be summarized as follows: High oxygen partial pressures avoid oxygen deficient films. On the other hand, energetic oxygen ions or neutrals cause an etching of the film surface, changing the metal stoichiometry of the films. Changing the substrate temperature has no effect on the film stoichiometry in the temperature range investigated here. However, increasing the substrate temperature results in larger grain sizes and the precipitation of an additional crystal phase. Substituting Si/SiO2 by Pt80Ir20 substrates allows to obtain crystalline NKN films already at temperatures as low as 300°C.

Furthermore, it was found that the mechanical and electrical performance of the films area strong function of their microstructure and chemical composition: The mechanical properties such as the Young's modulus and the hardness improve by improving the crystalline quality of the NKN films, and the highest dielectric constants are obtained for stoichiometric films.

Place, publisher, year, edition, pages
Linköping: Linköping University, 2003. p. 47
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 844
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:liu:diva-179076 (URN)9173737437 (ISBN)
Public defence
2003-10-30, hörsal Planck, Fysikhuset, Linköpings universitet, Linköping, 10:15
Opponent
Note

All or some of the partial works included in the dissertation are not registered in DIVA and therefore not linked in this post.

Available from: 2021-09-10 Created: 2021-09-10 Last updated: 2023-03-01Bibliographically approved

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Kugler, Veronika MozhdehSöderlind, FredrikMusic, DenisHelmersson, Ulf

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