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Investigation of Nbnx Thin Films and Nanoparticles Grown by Pulsed Laser Deposition and Thermal Diffusion

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Investigation of Nbnx Thin Films and Nanoparticles Grown by Pulsed Laser Deposition and Thermal Diffusion Old Dominion University ODU Digital Commons Electrical & Computer Engineering Theses & Dissertations Electrical & Computer Engineering Winter 2013 Investigation of NbNx Thin Films and Nanoparticles Grown by Pulsed Laser Deposition and Thermal Diffusion Ashraf Hassan Farha Old Dominion University Follow this and additional works at: https://digitalcommons.odu.edu/ece_etds Part of the Condensed Matter Physics Commons, Electrical and Computer Engineering Commons, and the Materials Science and Engineering Commons Recommended Citation Farha, Ashraf H.. "Investigation of NbNx Thin Films and Nanoparticles Grown by Pulsed Laser Deposition and Thermal Diffusion" (2013). Doctor of Philosophy (PhD), Dissertation, Electrical & Computer Engineering, Old Dominion University, DOI: 10.25777/8tmf-wg54 https://digitalcommons.odu.edu/ece_etds/180 This Dissertation is brought to you for free and open access by the Electrical & Computer Engineering at ODU Digital Commons. It has been accepted for inclusion in Electrical & Computer Engineering Theses & Dissertations by an authorized administrator of ODU Digital Commons. For more information, please contact [email protected]. INVESTIGATION OF NbNx THIN FILMS AND NANOPARTICLES GROWN BY PULSED LASER DEPOSITION AND THERMAL DIFFUSION by Ashraf Hassan Farha B.Sc. June 1999, Ain Shams University, Egypt M.Sc. February 2004, Ain Shams University, Egypt A Dissertation Submitted to the Faculty of Old Dominion University in Partial Fulfillment o f the Requirements for the Degree of DOCTOR OF PHILOSOPHY ELECTRICAL AND COMPUTER ENGINEERING OLD DOMINION UNIVERSITY December 2013 Approved by: Ham tiisayeu-/\ii ^uirecior) Helmut Baumgarm Mfember) 'on Namkoong (Member) _______ Ganapati Myneni (Member) ABSTRACT INVESTIGATION OF NbNx THIN FILMS AND NANOPARTICLES GROWN BY PULSED LASER DEPOSITION AND THERMAL DIFFUSION Ashraf Hassan F arha Old Dominion University, 2013 Director: Dr. Hani Elsayed-Ali Niobium nitride films (NbNx) were grown on Nb and Si (100) substrates using pulsed laser deposition (PLD), laser heating, and thermal diffusion methods. Niobium nitride films were deposited on Nb substrates using PLD with a Q-switched Nd: YAG laser (X = 1064 nm, 40 ns pulse width, and 10 Hz repetition rate) at different laser fluences, different nitrogen background pressures and deposition temperatures. The effect of changing PLD parameters for films done by PLD was studied. The seen observations establish guidelines for adjusting the laser parameters to achieve the desired morphology and phase of the grown NbNx films. When the fabrication parameters are fixed, except for laser fluence, surface roughness, deposition rate, nitrogen content, and grain size increases with increasing laser fluence. Increasing nitrogen background pressure leads to change in the phase structure of the NbNx films from mixed -Nb 2N and cubic 5-NbN phases to single hexagonal P- Nb2N. A change in substrate temperature led to a pronounced change in the preferred orientation o f the crystal structure, the phase transformation, surface roughness, and composition of the films. The structural, electronic, and nanomechanical properties of niobium nitride PLD deposited at different nitrogen pressures (26.7-66.7 Pa) on Si(100) were investigated. The NbNx films exhibited a cubic 8-NbN with a strong (111) orientation. A correlation between surface morphology, electronic, and superconducting properties was found. The highly-textured 8-NbN films have a Tc up to 15.07 K. The film was deposited at a nitrogen background pressure of 66.7 Pa exhibited improved superconducting properties and showed higher hardness values as compared to films deposited at lower nitrogen pressures. NbN nanoclusters that were deposited on carbon coated Cu-grids using PLD at laser fluence o f 8 J/cm2 were observed. Niobium nitride is prepared by heating o f Nb sample in a reactive nitrogen atmosphere (133 Pa) at a temperature of 900 °C. The results suggest that the niobium nitride was crystalline in the single phase o f hexagonal /?-Nb 2N. As heating time increased, film growth continued with improvement in hardness and modulus. The XRD of samples prepared by a thermal diffusion method at low nitrogen pressure and high temperatures were reported. The samples were prepared at temperatures ranging from 1250-1500 °C. 2D-XRD images of samples, processed at temperature range from 1250 -1500 °C at pressure o f 1.3x1 O'3 Pa, showed the formation of an a phase. As pressure increased to 0.13 Pa, an a-NbN phase mixed with P-Nb 2N phase appeared. Niobium nitride samples were prepared by laser nitridation using a Q-switched Nd: YAG nanosecond laser and Ti: sapphire femtosecond lasers. The effects o f laser fluence on the formed phase, surface morphology, and electronic properties of the NbNx were investigated. Samples were prepared using Nd: YAG laser are o f NbNx in the cubic 8-NbN phase. The femtosecond laser-nitrided samples were prepared by different laser fluences of 0.1-1.3 mJ/cm2 at 4.0><104 Pa nitrogen pressure. NbNx samples with mixeda, (3 and 8 phases were observed. The cubic 8-NbN structure is dominated over the other two phases. This dissertation is dedicated to my parents, my wife Samira, and my children: Mohamed, Rawda and Rana. ACKNOWLEDGEMENTS I would like to express my profound gratitude and appreciation to my advisor Prof. Dr Hani Elsayed-Ali. I appreciate all his contributions, ideas, funding and invaluable support that make my PhD studies fruitful. He was my biggest chance during my academic working out at ODU. His expertise on the subject and critical feedback strengthen the thesis and see it through to completion. It has been an honor to work with such a kind of successful scientist and professor. Also I need to express my many thanks to my country Egypt for granted me this PhD scholarship and financial support I got to study in US. I particularly thank to Prof. Yuksel Ufuktepe who increased our productivity and his positive encouragement help, and for all his contributions that I couldn’t be very successful without his supervision and experience. I'd like to thank my entire committee Dr Helmut Baumgart, Dr Gon Namkoong and Dr Ganapati Myneni for taking the time to review my dissertation and providing valuable insight and suggestions. My thanks and gratitude goes to my family, back home in Egypt, for all their love, inspiration and prayers for me, especially my mother Fathia Mahgoub and my father Saeed Farha who raised; loved and supported me in all my life. Words cannot express my love and thanks for them. Lastly, I want to express my grateful, love and acknowledgments to my wife Samira Abdel Aziz whom I love. Thanks for her continuous love and supports she did during my studying for PhD. And I am thankful for my children, Mohamed Farha, Rawda Farha and Rana Farha, whom I love. I can’t imagine a life without them. I wish them all my best in their life. TABLE OF CONTENTS LIST OF TABLES......................................................................................................................... viii LIST OF FIGURES..........................................................................................................................ix CHAPTER I: INTRODUCTION....................................................................................................1 1.1. BACKGROUND AND MOTIVATION..................................................... 1 CHAPTER II: OVERVIEW ON NIOBIUM AND NIOBIUM NITRIDE SUPERCONDUCTOR MATERIALS.......................................................................................... 7 11.1. INTRODUCTION.........................................................................................7 11.2. Nb AND NbN SUPERCONDUCTOR MATERIALS.........................11 11.3. NbNx THIN FILM PREPARATION METHODS.................................16 II.3.1. NbNx FILM FABRICATION.................................................................17 CHAPTER III: THIN FILM GROWTH BY PULSED LASER DEPOSITION............... 22 III. 1. INTRODUCTION..................................................................................... 22 III.2. MECHANISM OF PLD ........................................................................... 26 CHAPTER IV: EXPERIMENTAL TECHNIQUES................................................................ 39 IV. 1. INTRODUCTION................................................................................... ..39 IV.2. PULSED LASER DEPOSITION SYSTEM........................................ 40 IV.3. CHARACTERIZATION TECHNIQUES.............................................41 CHAPTER V: PULSED LASER DEPOSITION OF NbNX THIN FILMS ON Nb SUBSTRATE...................................................................................................................................50 V.l. INTRODUCTION.......................................................................................50 V.2. EXPERIMENTAL DETAILS...................................................................52 V.3. RESULTS AND DISCUSSION...............................................................54 V.4. CONCLUSIONS.........................................................................................90 CHAPTER VI: PROPERTIES OF NIOBIUM NITRIDES PREPARED BY REACTIVE THERMAL DIFFUSION.............................................................................................................. 92 VI. 1. INTRODUCTION..................................................................................... 92 VI.2. EXPERIMENTAL SETUP......................................................................94
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