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Abstract In the Name of Allah, the Beneficent, the Merciful. First and foremost, I would like to glorify Allah for His blessing given to me throughout my study and in completing my Ph.D. thesis. I would like to express my special thanks of gratitude to my main supervisor Prof. Dr. Arafa Hassen, Professor of materials science, Physics Department, Faculty of Science, Fayoum University, and Vice President for Postgraduate Studies and Research, Fayoum University for giving me the opportunity to do research and providing invaluable guidance throughout this research. His dynamism, vision, sincerity, and motivation have deeply inspired me. He has taught me the methodology to carry out the research and to present the research works as clearly as possible. It was a great privilege and honor to work and study under his guidance. I am extremely grateful for what he has offered me. I would also like to thank him for his friendship, empathy, and great sense of humor. My sincere thanks to Prof. Dr. Mahmoud Abdel- Hafiez, Researcher at the Department of Physics, Harvard University, USA, and Uppsala University, Sweden for his valuable assistance from the beginning of my Ph.D. thesis and for offering me the internship opportunities at Heidelberg and Goethe University, Germany, and earn experience and knowledge from him and his group. It was a great honor to work under his guidance and learn from him. I would like to thank the rest of my thesis supervision committee, Dr. Abdelwahab Hassan and Dr. Tarob Abdelbasit. I acknowledge the financial support (Grant No. 23023) received from Science, Technology and Development Fund (STDF) Egypt (GERF funding program). IV I am extremely grateful to my mother and my dead father for their love, prayers, care, and sacrifices in educating and preparing me for my future. I am very much thankful to my wife for her love, understanding, prayers, and continuing support to complete this research work and my darling daughter Layan. Also, I express my thanks to my sisters, and brothers for their support and valuable prayers. |