All-solution Synthesized High-performance 2D Bi2O2Se Thin-film Transistor

다국어 초록 (Multilingual Abstract)

Two-dimensional (2D) semiconductors have emerged as a next-generation electronic material because of their excellent electrical and mechanical properties in the atomically thin regime. These materials with a van der Waals layered structure are particularly promising for emerging electronics capable of heterogeneous integration and flexibility. For this purpose, low-temperature, and high-quality synthesis of 2D semiconductors are essential, wet chemical synthesis has remarkable advantages in low process temperature, scalability, and cost-effectiveness compared to conventional chemical vapor deposition processes. However, it remains a considerable challenge to achieve high quality and device performance. Here, we report the wet chemical synthesis via a bottom-up process of 2D Bi2O2Se semiconductors showing a high mobility characteristic. The all-solution-based processes are carried out at a low temperature below 200 ℃ producing free-standing 2D flakes with a lateral size of over 10 μm and thickness down to 8 nm. In addition, the single-crystalline Bi2O2Se channel in a back-gated field-effect transistor geometry exhibited high mobility up to 132 cm2V-1s-1 at room temperature. Notably, this solution can be assembled into a thin film for large-area device fabrication through a simple method such as liquid/air interface self-assembly. Our demonstration provides an innovative bottom-up synthesis approach to preparing high-quality semiconductors cost- and energy-effectively.

목차 (Table of Contents)

• TABLE OF CONTENTS
• ABSTRACT 2
• 국문 초록 3
• TABLE OF CONTENTS 6
• LIST OF TABLES 8
• LIST OF FIGURES 9
• CHAPTER 1. INTRODUCTION 11
• 1.1 Thin-film Transistor: State-of-the-art Progresses and Challenges 11
• 1.2 Advantages and Challenges of 2D Semiconducting Materials for TFT Application 19
• 1.3 Emerging 2D Semiconducting Material: Bi2O2Se 25
• 1.3.1 High Carrier Mobility 29
• 1.3.2 Flexibility 31
• 1.3.3 Low Process Temperature 34
• CHAPTER 2. WET-CHEMICAL BOTTOM-UP SYNTHESIS METHOD 39
• 2.1 Synthesis Procedures 39
• 2.1.1 Hydrothermal Reaction Parameters 42
• 2.1.2 Reaction Mechanism 44
• 2.1.3 Temperature and Reaction Time 47
• 2.2 Large-area Thin-film Fabrication and Characterization 48
• CHAPTER 3. ANALYSIS METHODOLOGY 52
• 3.1 Crystallinity and Structure Analysis: Optical images, Atomic Force Microscope (AFM) Analysis, Raman Spectra, X-ray Diffraction Pattern (XRD), and Selected Area Electron Diffraction (SAED) Pattern 52
• 3.2 Elemental Composition Analysis: X-ray Photoelectron Spectroscopy (XPS) and Energy Dispersive Spectrometry (EDS) Mapping 54
• CHAPTER 4. ELECTRICAL CHARACTERIZATION OF BI2O2SE FET 58
• 4.1 Device Fabrication Procedures and Electrical Properties Analysis 58
• CHAPTER 5. CONCLUSION 62
• 5.1 Summary 62
• 5.2Future Work and Perspectives 63
• REFERENCES 65