Synthesis of niobium compounds by CVD and epitaxial growth

다국어 초록 (Multilingual Abstract)

Chemical Vapor Deposition (CVD) method is widely used for high quality synthesis of nanomaterials such as graphene, CNT, and MoS2. However, CVD synthesis for Niobium compounds (Niobium oxide, Niobium carbide, Niobium selenide), especially Niobium selenides, has not been studied much.
Niobium oxide (Nb2O5) can be used for various applications including gas sensors, photo-catalysts, photo-detectors, batteries, and solar cell. Also, Niobium carbide (NbC) is promising for various applications such as a reinforced phase in an iron matrix, hard coating, and wear protection. In case of Niobium selenides, NbSe2 and NbSe3 are well known materials because they exhibit interesting physical properties like the presence of both superconductivity (SC) and charge density waves (CDW) and the competition between SC and CDW. In this study, we aimed to study on CVD　synthesis of Niobium compounds Furthermore, all three compounds have grown epitaxially on c-plane sapphire substrates, and the mechanism for the epitaxial growth will also be discussed.

목차 (Table of Contents)

• Chapter 1. Synthesis of Niobium Oxide (Nb2O5) 1
• 1. Introduction 1
• 2. Experimental 3
• 2.1 Growth of Niobium Oxide (Nb2O5) 3
• 2.2 Analysis and Measurement 3
• 3. Results and Discussion 4
• 3.1 Morphology and Structural Characterization 4
• 3.2 Epitaxial Growth Mechanism 8
• 3.3 Optical Property Characterization 10
• 3.4 Photocurrent Property Characterization 12
• 4. Conclusion 14
• Chapter 2. Synthesis of Niobium Carbide (NbC) 17
• 1. Introduction 17
• 2. Experimental 18
• 2.1 Growth of Niobium Carbide (NbC) 18
• 2.2 Analysis and Measurement 21
• 3. Results and Discussion 22
• 3.1 Morphology and Structural Characterization 22
• 3.2 Epitaxial Growth Mechanism 27
• 3.3 Mechanical Property Characterization 30
• 4. Conclusion 33
• Chapter 3. Synthesis of Niobium Selenide (NbxSey) 36
• 1. Introduction 36
• 2. Experimental 38
• 2.1 Growth of Niobium Selenide (NbxSey) 38
• 2.2 Analysis and Measurement 41
• 3. Results and Discussion 41
• 3.1 Temperature dependence of Niobium Selenide (NbxSey) Growth 41
• 3.2 Se supply dependence of Niobium Selenide (NbxSey) Growth 44
• 3.3 Epitaxial Growth Mechanism 47
• 4. Conclusion 50
• References 51
• 논문요약 63