近期以來，介面研究成為熱門的議題，因為材料的尺寸不斷縮小，造成介面特性的重要性比重日益增加。在本研究中，利用剖面掃描穿隧顯微鏡觀察奈米材料同物質(不同物理特性)接面間的介面電子特性。
本文的研究主題主要探討多鐵性材料 BiFeO3域壁的電子特性。內容包含了四個研究成果：(1)在BiFeO3的71度域壁，因為具有較小的能隙造成導電的同質介面。(2) BiFeO3上的109度域壁，與71度域壁相比，因擁有較小的能隙，表現出比71度域壁更導電的現象。(3)材料成長上，利用基板的晶格結構可控制多鐵性材料BiFeO3域壁的結構方式。量測結果上，在BiFeO3基板上成長90度域壁，發現其能帶邊界的變化程度是不同於71度與109度的變化。 (4)利用BiFeO3為基底，域壁與電域的存在影響鐵磁性材料La0.7Sr0.3MnO3薄膜出現域壁，且其域壁的能隙比La0.7Sr0.3MnO3本身的電域縮小0.3eV。同時，研究期間亦參與在重摻雜硫的矽晶體上，發現有絕緣態轉金屬態的現象。在存有金屬態的區域上，發現雜質能帶的產生。相關結果同時附錄在本論文中
利用這些資訊可以知道同質介面在材料中的影響範圍及電子特性，進而對未來奈米材料的應用及研究方向提供直接量測的資訊。

Recently, downsizing of the device causes the ratio of the interface to increase, which subsequently makes the research on interface characteristics more important. In this work, the electronic properties of the homo-interfaces are studied using cross-sectional scanning tunneling microscopy (XSTM).
The thesis includes the following four topics on multiferroic materials, BiFeO3. The evolution of the electronic structures across the domain walls in BiFeO3 is investigated by XSTM. (1) At 71° domain wall of BiFeO3, experimental results show that the decrease of the energy band gap induces the conductive homo-interface. (2) Compared with 71° domain wall, 109° domain wall of BiFeO3 has the smaller energy band gap. (3) 90° domain wall is found on BiFeO3 because the substrate effect alters the a/c ratio of BiFeO3 thin film. The decrease variation of the energy band edge at 90° domain wall is different to that at 71° domain wall and 109° domain wall. (4) Due to the domain wall of BiFeO3 at the La0.7Sr0.3MnO3/ BiFeO3 system, the domain wall is generated on the ferromangentic material La0.7Sr0.3MnO3. The energy band gap on the domain wall of La0.7Sr0.3MnO3 is ~0.7 eV, which is smaller than the mid-domain about 0.3 eV. In addition, in this thesis, the evolution of the electronic structures across the homo-interface of the dopant distribution on supersaturated sulfur-doped silicon is also discussed. The insulator-to-metal transition is directly observed in our experiment. In addition, the impurity band of the supersaturated sulfur-doped system is also demonstrated by using STM local measurements.
The electronic properties provide the information for future applications and researches.

中文摘要 I
Abstract II
致謝 IV
Table of contents V
List of figures captions VII
Chapter 1 Introduction 1
1.1 Interfaces 1
1.2 Homo-interfaces 2
Chapter 2 Experimental instrumentations and methods 5
2.1 Cross-sectional scanning tunneling microscopy 5
2.2 Principle of scanning tunneling microscopy 7
2.3 Principle of scanning tunneling spectroscopy 10
2.3.1 Physical meaning of dI/dV 10
2.4 Scanning tunneling microscopy operating mode 11
2.5 Tip preparation 15
2.6 Theory calculation：Considering the tip-induced band bending effect (TIBB) 16
Chapter 3 The 71° domain wall at the multiferroic material, BiFeO3 [45] 21
3.1 Introduction 21
3.2 Sample preparation 24
3.3 STM Results and discussion 25
3.3.1 Topographic and electronic property at SrTiO3 substrate 25
3.3.2 Confirmation the interface location between BiFeO3 and Nb-doped SrTiO3 26
3.3.3 Analysis of the electronic properties across 71° domain wall 28
3.4 Summary 32
Chapter 4 The 109° domain wall at the multiferroic material, BiFeO3 [45] 33
4.1 Introduction 33
4.2 Sample preparation 33
4.3 STM Results and discussion 34
4.3.1 Analysis of the electronic properties across the 109° domain wall 34
4.4 Summary 38
Chapter 5 The 90° domain wall at the multiferroic material, BiFeO3 [66] 39
5.1 Introduction 39
5.2 Sample preparation 41
5.3 STM Results and discussion 42
5.3.1 Analysis of the electronic properties at the InTiO3/BiFeO3/NdScO3 interfaces 42
5.3.2 Analysis of the electronic properties across the 90° domain wall 44
5.4 Summary 46
Chapter 6 The domain wall at the ferromagnetic material, La0.7Sr0.3MnO3 47
6.1 Introduction 47
6.2 Sample preparation 48
6.3 STM Results and discussion 49
6.3.1 Topographic and electronic properties at the La0.7Sr0.3MnO3/BiFeO3/DyScO3 interface 49
6.3.2 Analysis of the electronic properties across the domain wall at La0.7Sr0.3MnO3 thin film 50
6.4 Summary 53
Chapter 7 Conclusions 55
Reference 57
Appendix A 62
A.1 The impurity band at the solar cell, S-doped Si [76] 62
A.1.1 Introduction 62
A.1.2 Sample preparation 63
A.1.3 STM Results and discussion 64
A.1.4 Summary 74
Publication list 75

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