PhD Thesis Arne Lüker final version V4 - Cranfield University

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iv To all my friends in Cranfield (in no particular order and sorry if I forgot one or two): Robert Wright, Carlos Fragkiadakis, Petros Gkotsis, Hannah Gardner, David Darbyshire, Glen Leighton, Silvana Corkovic, Diego Gallardo, Debu Bhattacharyya, Emma Worthington, Paul Jones and Ghazal Hakemi, thank you! It was a pleasure to know you, and I wish you all the best for your future, wherever it will lead you. Hopefully we see us again sometimes - somewhere. Special thanks go to Andrew Stallard and Matthew Taunt for their never ending effort to keep our labs running. You are doing a marvelous job, guys! And thank you for your jump lead, Andy! I want to thank also the panel of my first and second year review: Dr. Robert Dorey and Dr. Robert Allwood as well as my internal examiner Dr. Zhaorong Huang and external examiner Prof. Dr. Bernd Ploss. They treated me critical but fair and always nice. I appreciated that. And sorry for the delay of these reviews. And I have to thank Peng Bao for his help with the measurements at high frequencies in Birmingham and fruitful discussions, and Andreas Fritz for printing and binding several copies of this thesis. But the biggest thank you goes to my parents, Inge and Rolf Lüker! I started school at seven and I am now 34. That means 27 years of hope and suffering, pride and worries, joy and tears and money spending. Who else would have endured all this for so long, except you? I love you and can not thank you sufficiently enough. This thesis is dedicated to you! I thank you all! Arne Lüker, Holsen, 29 th of November 2009
Table of Content Introduction and Motivation ............................................................................................... 7 Historical Remarks............................................................................................................ 12 1.1 A Short History of Ferroelectricity ................................................................... 12 1.2 A Short History of Sol-Gel ............................................................................... 20 1.3 Materials for Tunable Applications – State of the Art ...................................... 23 1.4 References ......................................................................................................... 27 Theoretical Considerations and Literature Review ........................................................... 32 2.1 Theory of the Dielectric Response of Tunable Materials ................................. 32 2.1.1 Dielectric Permittivity ................................................................................... 32 2.1.2 Tunability ...................................................................................................... 34 2.1.3 Figure of Merit .............................................................................................. 36 2.2 Dielectric Loss in Ferroelectrics ....................................................................... 37 2.2.1 Intrinsic Losses ............................................................................................. 37 2.2.2 Extrinsic Losses ............................................................................................ 40 2.4 Crystallography of Perovskites ......................................................................... 43 2.4.1 The crystal structure of perovskite ................................................................ 43 2.4.2 Electronic and Magnetic Properties of Perovskites ...................................... 48 2.5 Sol-Gel Chemistry ............................................................................................ 54 2.5.1 Solution Preparation...................................................................................... 54 2.5.2 Film Deposition ............................................................................................ 59 2.5.3 Gel to Ceramic Conversion ........................................................................... 63 2.6 References ......................................................................................................... 64 Characterisation of Ferroelectric Thin Films .................................................................... 70 3.1 Sputter deposition and Thermal Evaporation ................................................... 71 3.1.1 Sputter Deposition ........................................................................................ 71 3.1.2 Thermal evaporation ..................................................................................... 72 3.2 Analysis............................................................................................................. 73 3.2.1 X-ray Diffraction Analysis (XRD) ............................................................... 73 3.2.2 Scanning Electron Microscopy (SEM) ......................................................... 74 3.2.3 Polarisation Hysteresis Measurement ........................................................... 75 3.2.4 Atomic Force Microscopy (AFM) ................................................................ 76 3.2.5 Curie Temperature Measurement ................................................................. 76 3.2.6 Auger Emission Spectroscopy (AES) ........................................................... 77 3.3 References ......................................................................................................... 79 Barium Strontium Titanate (BST) .................................................................................... 81 4.1 A Short Review of BST Deposition.................................................................. 82 4.2 Synthesis and Characterisation of BST............................................................. 85 4.3 Discussion ......................................................................................................... 89 4.4 References ......................................................................................................... 92 Lead Strontium Titanate (PST) ......................................................................................... 95 5.1 Synthesis and Crystallisation of PST ................................................................ 96 5.2 Dielectric Properties of PST 50/50 ................................................................. 100 5.3 PST 50/50 Varactors with Copper Electrodes ................................................ 102 5.4 References ....................................................................................................... 107 v
Page 1 and 2: Sol-Gel derived Ferroelectric Thin
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Page 5: Acknowledgements I want to take thi
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Sol-Gel derived Ferroelectric Thin
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Intensity [arb. Units] (g) (f) (e)
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Relative diel. diel. constant Const
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Intensity [arb. Units] Intensity [a
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Tunability [%] 100 90 80 70 60 50 4
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(g) (f) (e) (d) (c) (b) (a) Sol-Gel
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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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