I would like to thank many people who have supported me during my study in Nanyang Technological University. First and foremost, I would like to express my sincere gratitude and appreciation to my supervisor, Assoc. Prof. Lim Meng Hiot, for his professional guidance and support, for his invaluable advice and encouragement throughout my Ph.D. program. I benefit a lot from his supervision over the years. I really appreciate his style of supervision and his patience to his students. I would like to appreciate Assoc. Prof. Ling Keck Voon, for his apparatus support and helpful discussions in my project. I also appreciate Mr. Sia Liang Poo, Mr.