Linköping University | Department of Physics, Chemistry and Biology Master Thesis, 60 hp | Educational Program: Chemistry Spring 2021 | LITH-IFM-A-EX—21/3948—SE Homebuilt Reactor Design and Atomic Layer Deposition of Metal Oxide Thin Films Pamburayi Mpofu Examiner, Professor Henrik Pedersen Supervisor, Associate Professor Urban Forsberg A thesis submitted in partial satisfaction of the requirements for the degree of MASTER OF SCIENCE in CHEMISTRY Specialization: Materials Science by Pamburayi Mpofu Department of Physics, Chemistry and Biology (IFM) Faculty of Science and Engineering (Institute of Technology) (LITH) Linköping University, Sweden Linköping, Sweden, June 2021 i Supervisor Associate Prof. Urban Forsberg Department of Physics, Chemistry and Biology (IFM) Linköping University Linköping, Sweden Examiner Prof. Henrik Pedersen Department of Physics, Chemistry and Biology (IFM) Linköping University Linköping, Sweden Opponent Pentti Niiranen Department of Physics, Chemistry and Biology (IFM) Linköping University Linköping, Sweden “It looks like our long run led rather to a start than to a completion – I am deeply impressed by the huge advance that has followed in the atomic layer deposition technology and the scope of its applications.” - Dr. Tuomo Suntola, 2014 ii Upphovsrätt Detta dokument hålls tillgängligt på Internet – eller dess framtida ersättare – under 25 år från publiceringsdatum under förutsättning att inga extraordinära omständigheter uppstår. 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For additional information about the Linköping University Electronic Press and its procedures for publication and for assurance of document integrity, please refer to its www home page: https://ep.liu.se/. © 2021, Pamburayi Mpofu iii Abstract This research thesis covers work done on building an atomic layer deposition (ALD) reactor followed by the development and optimization of an ALD process for indium oxide thin films on crystalline silicon substrates from new precursors using this new homebuilt cost-effective tool. This work describes the design, building and testing of the ALD system using an indium triazenide precursor and water in a novel precursor combination. The reactor was built to be capable of depositing films with comparable results to commercially built systems. Indium oxide thin films were deposited as the deposition temperature was varied from 154 to 517 0C to study the effects of deposition temperature on the obtained film thicknesses and ascertain the ALD temperature window between 269-384 0C. The presence of indium oxide films was confirmed with X-ray diffraction analysis, which was also used to study their crystallinity. The films were found to have a polycrystalline structure with a cubic phase. Measurement of film thickness was performed using X-ray reflectivity which determined a growth rate of approximately 1 Å/cycle. Elemental composition was determined by X-ray photoelectron spectroscopy which confirmed contamination-free indium rich films. Scanning electron microscope imaging was used to examine the surface morphology of the films as well as thick cross-sectional thicknesses. Since indium oxide films are potentially useful in various electronic, optical, and catalytic applications, emphasis is also placed on the accurate characterization of the chemical and physical properties of the obtained thin films. Optical and electrical properties of the produced transparent conducting oxide films were measured for transparency (and optical band gap) and electrical characterization by resistivity measurements, from UV- Vis spectrophotometry and 4-point probe data respectively. A high optical transmission >70 %, a wide band gap 3.99-4.24 eV, and low resistivity values ∼0.2 mΩcm, showed that In2O3 films have interesting properties for various applications confirming indium oxide a key material in transparent electronics. iv Acknowledgements The research leading to results of this thesis work was carried out and supported by The Pedersen Research Group, led by Professor Henrik Pedersen in the Department of Physics, Chemistry and Biology (IFM) at Linköping University in Sweden between September 2020 and June 2021 as part of my 2-year MSc in Chemistry journey that began in August 2019. I would like to express my big thanks to Prof. Pedersen for introducing me to the world of CVD-ALD, welcoming and awarding me the opportunity to conduct research work with his team. I am also totally grateful to my supervisor and tutor Ass. Professor Urban Forsberg. I appreciate his never-ending professional support, mentorship, very constructive and fruitful cooperation, and cheerful attitude since the first day of my thesis work. I do not think I could have had a better mentor. Thank you, Urban, for all your help! During my project, I had the privilege of working with brilliant scientists in the research group. It is because of their fruitful collaboration that this work led to the result of publishable scientific work. I would want to thank these colleagues for their support, helpfulness, creativity, patience, and friendship, particularly my office mates Polla Rouf (thanks for your priceless assistance, the XRD, SEM, XPS and various instrumentation that you taught me) and Pentti Niiranen, for the fun office spirit. Working in this CVD-ALD research group has been a privilege and great fun. I wish to thank the former and current members of the group for creating such a wonderful work environment. A big thanks goes to all the other MSc Chemistry students, class of 2021, at IFM for maintaining an extraordinarily friendly and pleasurable working atmosphere. I gratefully acknowledge the financial support of the Swedish Institute through the Swedish Institute Scholarship for Global Professionals (SISGP) for fully funding my 2-year MSc studies. v Finally, I want to thank my family for all the support during the past 2 years that I have been in Sweden studying at Linköping University. I am grateful for all the prayers, wishes and encouragement from my parents Anos and Elizabeth. Last, but certainly not least, I wish to thank and appreciate my wife Amina for all the love and understanding, and our son Kayden for being the sunshine of my life. Linköping, June 2021 Pamburayi Mpofu vi Table of Contents Upphovsrätt ........................................................................................................................................................................ iii Copyright ............................................................................................................................................................................. iii Abstract ................................................................................................................................................................................ iv Acknowledgements ........................................................................................................................................................ v Table of Contents .......................................................................................................................................................... vii Table of Figures ............................................................................................................................................................... ix List of Tables ..................................................................................................................................................................... xi List of Abbreviations .................................................................................................................................................. xii 1. INTRODUCTION .....................................................................................................................................................