밀도 범함수 이론을 이용한 저차원 재료와의 금속 접촉에 관한 이론적 연구 = Theoretical Study on Metal Contacts to Low-Dimensional Materials Using Density Functional Theory

다국어 초록 (Multilingual Abstract)

Two-dimensional (2D) materials have drawn attention as potential alternatives to conventional Si-based electronics due to their atomic thickness, superior electrostatics, and tunable properties. Despite these advantages, 2D materials often exhibit degraded performance at the metal contact interface, deviating from theoretical expectations. This discrepancy is primarily driven by Fermi level pinning (FLP), which originates from metal-induced gap states (MIGS) and defect-induced gap states (DIGS) at the interface. These gap states effectively suppress the tunability of the Schottky barrier height, limiting the efficiency of carrier injection and device operation. In this study, we provide a comprehensive review of the underlying mechanisms responsible for FLP in 2D material–metal junctions, based on insights obtained from first-principles calculations using density functional theory (DFT). We examine how interfacial chemical bonding, atomic-scale defects, and van der Waals versus direct contacts contribute to the emergence of gap states. We also discuss how strain engineering, contact geometry, and electronic screening influence the interface properties and propose strategies to suppress FLP. The goal of this work is to identify key factors that govern contact behavior and to suggest practical design rules for achieving low-resistance, high-performance 2D electronic devices.

목차 (Table of Contents)

• Ⅰ. Introduction 1
• Ⅱ. Background 4
• 2.1. 2D Materials 4
• 2.2. Fermi Level Pinning in 2D Materials 9
• 2.3. Density Functional Theory 14
• Ⅲ. Experiments 16
• 3.1. DFT Calculations 16
• 3.2. Construction of heterostructures 17
• Ⅳ. Results and Discussion 18
• 4.1. Electronic Structure of Monolayer MoS2 and MoS2-Metal Interfaces 18
• 4.2. Construction of MoS2-Metal heterostructures 22
• 4.3. Schottky Barrier Heights and Interfacial Charge Transfer 32
• Ⅴ. Conclusion 36
• Ⅵ. References 38
• 국 문 초 록 43
• Publications 45
• Acknowledgement 46