PhD Thesis Arne Lüker final version V4 - Cranfield University

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80 I love fools' experiments. I am always making them. Charles R. Darwin In Francis Darwins “The Life of Charles Darwin”, 1902 Kohn's Second Law: An experiment is reproducible until another laboratory tries to repeat it. Alexander Kohb In N Sreedharans “Quotations of Wit and Wisdom”, 2007 You make experiments and I make theories. Do you know the difference? A theory is something nobody believes, except the person who made it. An experiment is something everybody believes, except the person who made it. Albert Einstein In Gerald Holtons, “The Advancement of Science, and Its Burdens”, (1986),
Sol-Gel derived Ferroelectric Thin Films for Voltage Tunable Applications Barium Strontium Titanate (BST) It should be well known by now that BaTiO3 is a ferroelectric perovskite and has been well studied in bulk ceramic form where the measured permittivities are well in the thousand (see Fig. 2.4). By substituting the the A-site atom (Ba-atom) with Sr the Curie temperature, TC, can be shifted down from 120°C to around room temperature (Fig. 1.12). The linear drop of TC is ca. 3.4°C per mol%. Therefore, 30 mol% Sr (x=0.3) would bring the TC of Ba1-xSrxTiO3 down to room temperature. Due to this fact BST was and still is an attractive candidate for voltage tunable devices like varactors, phase shifters, DRAMs etc., where the ferroelectric crystal or thin film should be in the paraelectric state viz. the operating temperature should be above TC. BST films are, like PST, polycrystalline. Their properties heavily depend on composition, stoichiometry, microstructure (grain size and size distribution), film thickness and homogeneity of the film. The BST or/and PST thin film growth method significantly affects the composition, stoichiometry, crystallinity, and grain size of the film and, consequently, its dielectric properties. A variety of techniques have been used to deposit these films (see introduction section of chapter 2.4). BST 60/40 was chosen as a starting material in this study because it is widely investigated and used for voltage tunable thin films. A wide range of publications makes it relatively easy to gain access in this topic. In this chapter a short review of BST deposition is given, followed by the description of the synthesis and characterisation of BST thin films developed in the beginning of this study. It concludes with a comparison between two different approaches of BST sol-gel synthesis, pointing out the dominant role of the interfacial layer and the capacitance- density. 81
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Sol-Gel derived Ferroelectric Thin
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Abstract Ferroelectric perovskite t
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Acknowledgements I want to take thi
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Table of Content Introduction and M
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Page 31 and 32: Sol-Gel derived Ferroelectric Thin
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Page 99 and 100: Intensity [arb. Units] (g) (f) (e)
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Intensity [arb. Units] Sol-Gel deri
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Internships: Sol-Gel derived Ferroe
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PhD Thesis Arne Lüker final version V4 - Cranfield University

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