Electronic and Magnetic Properties of 2D Materials: A first principles study
- Alternative Title
- 2차원 물질의 전기적∙자기적 성질에 관한 제일원리연구
- Abstract
- In this era, material science progress depends on the discovery of new materials and understand their properties. 2D materials are compounds with reduced dimensionality, which often display unexpected physical and chemical properties. In this thesis, electronic and magnetic properties of 2D materials like graphene, beyond graphene and their hybrid structures will be examined.
This thesis will emphasis on Graphene, Graphitic carbon nitride (g-C4N3) and Phosphorene (monolayer of black phosphorus). These three materials has quite different physical, electronic and magnetic properties. For practical device applications, each material is experiencing different
problems. In this thesis, we will examine their physical properties as well as try to address the main issues and their solutions by using first principles calculations.
Indeed, the free standing graphene shows remarkable electronic, thermal, optical, mechanical and transport properties. However, zero-bandgap limited its advantages to use it in semiconductor industry. This thesis will provide a way to open a bandgap in graphene. Furthermore this thesis also explore the possibility to use graphene for tunneling magnetoresistance (TMR) structure. Thus, Chapter 3 presents the thickness dependent band gap and effective mass of BN/graphene/BN and potential spintronics in Graphene/BN/Co(111) structure.
Graphitic carbon nitride (g-C4N3) metal free material showed half metallic properties in the free standing state. For spintronics, it is of interest to examine ferromagnetism in pure 2p electron because of large spin relaxation time is expected owing to the relatively weak spin-orbit coupling.
In this thesis, we will to propose physical structural and magnetic properties of the multilayer g-C4N3, hybrid structure and manipulation of electronic and magnetic properties of g-C4N3. Hence, Chapter 4 presents the spin-dependent transport and Optical Properties of Half-Metallic g‐C4N3 Films, Boron nitride (BN) ideal substrate for g‐C4N3 and transition from half metal to semiconductor in doped g-C4N3.
Very recently, a new two-dimensional system, so-called phosphorene, was mechanically exfoliated by scotch tape based microcleavage from layered bulk black phosphorus. Phosphorene is a non-magnetic semiconductor with highly anisotropic electrical, mechanical and optical properties. However, the magnetism of phosphorene still remains an open question. In this thesis, we will explore the possibility to find magnetism in phosphorene, as well as phosphorene hybrid structure with graphene. Therefore, Chapter 5 investigates the Transition Metal Doped Phosphorene, magnetic property of porous black phosphorene layer and Graphene/phosphorene bilayer for high electron speed.
- Issued Date
- 2016
- Awarded Date
- 2016. 2
- Type
- Dissertation
- Publisher
- 부경대학교 대학원
- Affiliation
- 부경대학교 일반대학원
- Department
- 대학원 물리학과
- Advisor
- 홍지상
- Table Of Contents
- 1. Introduction of 2d materials ........................................................................................................ 1
1.1 Graphene ............................................................................................................................... 2
1.2 Graphitic Carbon Nitride (g-C4N3) ....................................................................................... 5
1.3 Phosphorene .......................................................................................................................... 9
2. Theory, Methodology & Computational Details ...................................................................... 13
2.1 Ab-initio, or first principle methods .................................................................................... 13
2.1.1 Density-functional Theory ............................................................................................ 14
2.1.2 The Hohenberg-Kohn Theorems .................................................................................. 15
2.1.3 Kohn-Sham Scheme ..................................................................................................... 17
2.1.4 Approximating Exchange and Correlation ................................................................... 18
2.2 Implementation in VASP .................................................................................................... 26
2.2.1 K-Point sampling .......................................................................................................... 26
2.2.2 Plane wave formalism .................................................................................................. 27
2.2.3 Cut-off energy............................................................................................................... 28
2.2.4 Projector Augmented-Wave method (PAW) ................................................................ 29
2.3 Computational Details ......................................................................................................... 29
2.4 Models of Different Systems ............................................................................................... 30
2.4.1 Models for Graphene: ................................................................................................... 30
2.4.2 Models for g-C4N3: ....................................................................................................... 30
2.4.3 Models for Phosphorene: .............................................................................................. 32
3. Graphene & Hybrid Structure for Bandgap & Spintronics ....................................................... 36
3.1 Thickness dependent band gap and effective mass of BN/graphene/BN ............................ 36
3.1.1 Introduction .................................................................................................................. 36
3.1.2 Results and Discussions................................................................................................ 37
3.1.3 Conclusion .................................................................................................................... 44
3.2 First-principles Study of Graphene on BN/Co(111): van der Waals Density Functional
Approach ................................................................................................................................... 46
3.2.1 Introduction .................................................................................................................. 46
3.2.2 Results and Discussions................................................................................................ 46
3.2.3 Conclusion .................................................................................................................... 56
4. Graphitic Carbon Nitride (g-C4N3) Intrinsic Half-Metal .......................................................... 57
4.1 Spin-Dependent Transport and Optical Properties of Transparent Half-Metallic g‐C4N3
Films .......................................................................................................................................... 57
4.1.1 Introduction .................................................................................................................. 57
4.1.2 Results and Discussions................................................................................................ 58
4.1.3 Conclusion .................................................................................................................... 68
4.2 Structural and Magnetic Properties of g-C4N3 on BN Substrate ......................................... 69
4.2.1 Introduction .................................................................................................................. 69
4.2.2 Results and Discussions................................................................................................ 69
4.2.3 Conclusion .................................................................................................................... 75
4.3 Transition from Half metal to Semiconductor in Li doped g-C4N3 .................................... 76
4.3.1 Introduction .................................................................................................................. 76
4.3.2 Results and Discussions................................................................................................ 76
4.3.3 Conclusion .................................................................................................................... 82
5. Phosphorene & Hybrid Structure .............................................................................................. 83
5.1 Transition Metal Doped Phosphorene: A First Principles Study ........................................ 83
5.1.1 Introduction .................................................................................................................. 83
5.1.2 Results and Discussions................................................................................................ 84
5.1.3 Conclusion .................................................................................................................... 93
5.2 Graphene/phosphorene bilayer: High electron speed, optical property and semiconductormetal
transition with electric field ............................................................................................. 94
5.2.1 Introduction .................................................................................................................. 94
5.2.2 Results and Discussions................................................................................................ 94
5.2.3 Conclusion .................................................................................................................. 105
5.3 Magnetism in Porous Phosphorene: Edge passivation & Electric field effect .................. 106
5.3.1 Introduction ................................................................................................................ 106
5.3.2 Results and Discussions.............................................................................................. 107
5.3.3 Conclusion .................................................................................................................. 119
6. Reference ................................................................................................................................ 120
7. Publications ............................................................................................................................. 131
- Degree
- Doctor
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