University of Groningen. Novel phases in ferroelectric BaTiO3 thin films Everhardt, Arnoud

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1 University of Groningen Novel phases in ferroelectric BaTiO3 thin films Everhardt, Arnoud IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite from it. Please check the document version below. Document Version Publisher's PDF, also known as Version of record Publication date: 2017 Link to publication in University of Groningen/UMCG research database Citation for published version (APA): Everhardt, A. (2017). Novel phases in ferroelectric BaTiO3 thin films: Enhanced piezoelectricity and low hysteresis [Groningen]: Rijksuniversiteit Groningen Copyright Other than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons). Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Downloaded from the University of Groningen/UMCG research database (Pure): For technical reasons the number of authors shown on this cover page is limited to 10 maximum. Download date:

2 Acknowledgements This piece of research, this thesis and all other developments would not have been possible without the help of an extensive amount of people who all contributed in one way or another. The first person I want to thank is Beatriz Noheda. As my promotor, supervisor and very kind person you have first of all made it possible to do this PhD at this position. But there is much more. You have not only helped guiding the research into the direction it has blossomed out to be, but you are also a mentor on more than research alone. With different personalities and working styles, you showed me another side of how things can be done, which has also enriched me as a person which is arguably even more difficult than the research itself. Your devotion to not only science, but also to the people behind it, even when it does not necessarily benefit only your own group, can be admired. I also want to thank Thom Palstra. You might have left your own research now for the benefit of all of science in this country, your view on research will never be forgotten. As my supervisor in both my bachelor and master thesis, you have shown me that science is not to be taken lightly. It is an important job to serve the world with the proper knowledge and you should always be extremely critical and cautious of your interpretations, your results, even yourself. It is a lesson that will never get lost. Also special thanks to Anne Arkenbout for showing me the first real steps into science back in my bachelor with contagious enthusiasm. While a research project usually starts quite lonely, with just you and your supervisor, we have managed to bring the joy of this topic to more people outside of this little research group. The longest collaboration has been with Sylvia Matzen. You started as a postdoc on many projects in our group, so obviously you were also assigned to be my postdoc. In a limited amount of time you managed to get all the projects in the group to work together well with lasting impact even when you moved to your beloved job in Paris. I can count myself lucky our collaboration did not end there, and you continued to help our project with endless comments on what we had been seeing. I would still have struggled now with small, tiny issues if it were not for you. I have also had the pleasure to collaborate with Neus Domingo and Gustau Catalan in Barcelona, who always welcomed me all those times I flew to you, ready to clog your PFM system day and night. Always willing to help with whatever weird ideas I came up with, not only for measurements on your system, but also conceptual ideas. Your devotion gave a real kick-start to all areas in my research. Umesh, I had the pleasure of meeting you for one day in which you gave a real start for the piezoelectric measurements, even though your measurements turned out not to be conclusive enough to be used in the thesis. Thibaud Denneulin, I am sad I have never met you in person, even though we have been in contact for more than three years. You started early on helping us with our films, and as our combined knowledge grew, you managed to get nice results, which turned out to be more amazing every time we tried something new. I hope to meet you in real life one day as you seem to be a very nice person as well. Thanks to Etienne Snoeck, Martin Hÿtch and Cesar Magen for the additional support on the TEM measurements. Yu-Tsun Shao and Jian-Min Zuo, your new TEM measurements were so important that they have been added to the last chapter of this thesis at the last possible moment, which increased its impact tremendously. Anna Grünebohm, we first met in a conference just in the beginning of my last year, but we turned it into an enormous discussion on the theory and experiments on these thin films. You are very knowledgeable, patient and able to explain for the hundredth time what we had discussed the week before. After my visit to you in Germany (as it is very close to home anyways) we thought we had finally figured everything out when everything changed again. I really enjoyed the endless 99

3 discussions and I wonder if the last word will ever be said. I do know now whom to contact if I ever need theory advice again. There have been a couple of other contacts I am grateful for. Jirka Hlinka, you have been very interested in our materials and were the first to contact me after my first oral presentation abroad. Our collaboration is not yet finished and I am sure something will come out of it in the future. Laurent Bellaiche, you have given us a good idea for a new direction of research which unfortunately we have not carried out yet because of substrate delivery problems. Paul Muralt and Robin Nigon, thank you for your advice on the measurement of piezoelectric materials. Dragan Damjanovic, thank you for your suggestions on our written manuscript. I am also grateful to my reading committee, Nava Setter, Guus Rijnders and Jeff de Hosson and I am honored that you have been willing to read this extensive thesis. Luckily not all contacts were from outside Groningen and also a lot of physical and mental help was received within this lovely place. Jeroen Heuver, you are always interested in other people and making sure that their research and equipment works, by working together for it. Saeedeh Farokhipoor, you are knowledgeable and passionate about science and have the ability to ask the right questions to get people thinking to the next level. Oleksiy Nesterov, we have worked together on similar materials and you helped me in getting started in the beginning on this new project for me. Justin Varghese, everyone always enjoyed your presence and I absolutely loved being able to visit you in Kerala in India (still the most lovely piece of earth I have ever been). Mart Salverda, I m still amazed by how fast you went from learning everything to being the main resource for people in the group for basically everything. You are too kind to everyone. Thank you too for checking chapter 2 of this thesis. Mónica Acuautla Meneses, an engineer in a research group doing fundamental science, what good can it bring? As it turns out, a lot of good things! It brings a lot of new learning for everyone, and with your help the energy harvesting chapter of this thesis has been improved a lot. Yingfen Wei, I have never seen someone failing with so much joy as you do, which is a real superpower that can only be underestimated, as it brings you to new heights that others cannot reach because they try to avoid failure. Jin Xu, only part-time group member, but nobody could be accepted more than you. I also want to thank all the other people I have interacted with in my time in this building. The cleanroom help with mainly Johan, Martijn and Eric, and all the other people with Aisha, Guowei, Anil, Laaya, Machteld, Geert, Liany, Graeme, Saurabh, Sander, Gaurav, Roald, Arijid, Paul, Alim, Alex, Mai, Lei, Shiva, Syarif and Tomas. Henriët van Mil-Boddeveld, you have helped me near the last phases of my PhD in ways I did not expect I would need when I started. Henk Bonder, we all like you very much, not only are you always ready to do what we ask within minutes, but you are also a very caring person for everyone. I am sure you will keep doing better. Jacob Baas, it does not matter if it is a broken bike, a broken soul or a broken theory or analysis, you will fix all those things for everyone. You are the social anchor of the group and a one-in-a-kind in this group. Jordi Antoja Lleonart and Silang Zhou, I was delighted to have you as my students. Not only did I have to try my best to teach you something about your topic and the practice of doing science, but also you have taught me something about teaching and about myself that I otherwise could not have learned. Jordi, exceptionally organized, teaching me to be even more consistent, and you have learned to get out of that box. Silang, you cannot be caught in a box, always trying out new things, you taught me to prepare for anything. Please keep on surprising the people around you. The group dynamics have been very interesting to be part of for those five full years (and up to seven years ago including my bachelor). Everyone brought their own personal input in the group process, and the group changed accordingly. Having lunch together, and important (unfortunately less urgent) tea o clock, or having food, drink and BBQ has been special all this time. I will miss all this, but hope you continue having as much fun as when I was around. 100

4 Acknowledgements Normaal gesproken wordt de financiering van een project niet genoemd in de acknowledgements van een these, maar in dit geval is het helemaal terecht om het wel te noemen omdat ik het niet als financiering beschouw. De Aduarderkring, een groep alumni van deze universiteit heeft besloten om mij te adopteren. Elk half jaar had ik het voorrecht om langs te mogen komen op de bijeenkomst van deze geweldige groep mensen. Ze komen oorspronkelijk bij elkaar om de binding met de universiteit weer iets op te zoeken, maar ze blijven bij elkaar omdat het zo n mooie en hechte groep is die in elkaar geïnteresseerd is. Ik voel me echt onderdeel van de familie en vind het jammer dat ik ze nu moet verlaten. Ze waren niet alleen geïnteresseerd in de toepassingen van mijn onderzoek (het onderzoek zelf is ook wel leuk, maar o zo lastig), maar ook in mij als persoon. En een beter compliment dan ik kom vooral voor jouw presentaties kan je niet krijgen. Ik moet ook de uitstekende leiding vanuit het Ubbo Emmius Fonds, met Josca Westerhof als grootste drijvende kracht achter dit project, bedanken, zonder wie dit allemaal nooit mogelijk was geweest. Het is niet alleen maar studeren en werken in Groningen geweest in al die 9 jaar. Ik heb ook heel veel plezier daarbuiten gehad met o.a. mijn duikclub Ad Fundum, het schaatsen bij Tjas, gewoon met andere promovendi omgaan bij Gopher en improviseren bij onze improgroep. En gelukkig heeft mijn familie ook geaccepteerd dat ik dit ben gaan doen, steun ondanks dat ze niets begrijpen van wat ik nu eigenlijk doe. Als laatste, bedankt Jolanda Heijnen voor alles wat je gedaan hebt, en alle vrijheid die je me gegeven hebt om al mijn rare plannen uit te voeren. Arnoud Everhardt La Paz, Bolivia (Februari 14, 2017) 101

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