拓撲絕緣體與磁性絕緣體的整合為研究自旋電子學和量子計算領域的新穎物理和技術應用提供了新的途徑。當拓撲絕緣體與磁性絕緣體組成異質結構時，拓撲表面態的時間反轉對稱性將透過磁鄰近效應被破壞並產生特殊現象，包括量子異常霍爾效應等熱門議題。量子異常霍爾效應會在霍爾電阻中形成一個量子化的台階，同時展現無耗散的傳輸。然而，如果沒有仔細的製造和清晰的界面來增強原子級的交換耦合，則可能出現磁化程度不穩定和薄膜品質無法重複的情況。本論文中，首先通過觀察反射式高能電子繞射振盪的行為來優化硒化鉍Bi2Se3的品質。在硒化鉍與α相氧化鋁異質結構(Bi2Se3/α-Al2O3)中獲得了優異的結晶性，其表現出15個反射式高能電子繞射振盪週期並且在電子傳輸結果中出現舒博尼科夫-德哈斯(Shubnikov-de Haas，SdH)振盪。其次，我們利用一種叫做硒緩衝低溫生長(Se-buffered low-temperature growth, SBLT growth)的技術在分子束磊晶系統中獲得優異結晶性c軸取向外延(c-axis epitaxial)的硒化鉍Bi2Se3薄膜在稀土鐵石榴石，如有垂直磁異向性的銩鐵石榴石(Tm3Fe5O12，TmIG)和有水平磁異向性的釔鐵石榴石(Y3Fe5O12，YIG)的磁性絕緣體薄膜上。亦可從硒化鉍Bi2Se3第一個五元組層開始的明亮且清晰的反射式高能電子繞射條紋表明稀土鐵石榴石和硒化鉍Bi2Se3之間的高品質界面，這即是研究界面交換耦合效應的要件之一。通過觀察硒化鉍與銩鐵石榴石異質結構(Bi2Se3/TmIG)中的異常霍爾效應和由硒化鉍Bi2Se3誘發的銩鐵石榴石(TmIG)和釔鐵石榴石(YIG)鐵磁共振場移位，表現出強烈的界面交換偶合作用。為了排除拓樸絕緣體中塊體態的貢獻，我們建構了三元拓樸絕緣體碲化鉍(Bi,Sb)2Te3。透過Hikami-Larkin-Nagaoka(HLN)方程式的擬合揭露了碲化鉍銻(Bi,Sb)2Te3中有兩個傳輸通道，實現了塊體態絕緣的特徵，且進一步利用角分辨光電子能譜證實此現象。在碲化鉍銻與銩鐵石榴石異質結構((Bi,Sb)2Te3/TmIG)中透過磁鄰近效應成功觀察到室溫可見的異常霍爾效應，這也是量子異常霍爾效應要在較高溫下實現的先決條件。在weak anti-localization被強烈抑制的情況下沒有觀察到負磁阻，此現象可能是因為塊體態絕緣薄膜中解耦的表面傳輸通道。我們的工作為以磁鄰近效應的方式實現量子異常霍爾效應奠定了基礎。

The integration of quantum materials like topological insulators (TIs) with magnetic insulators (MIs) offers a new approach to investigate the novel physics and technological applications in the field of spintronics and quantum computing. When TI interfaced with the MI layer, the time-reversal-symmetry of topological surface states would break via magnetic proximity effect (MPE) and generate exotic phenomena including the feverish topic of quantum anomalous Hall effect (QAHE). QAHE conducts a quantized plateau in Hall resistance and exhibits the dissipationless transport at the same time. However, without careful fabrication and sharp interface to enhance the atomic-scale exchange coupling, the challenges of large deviation in the degree of magnetization and non-reproducible film quality may arise. In this work, we first aimed to the optimization of the well-known 3D TI, Bi2Se3, film quality by observing the behaviors of reflection high-energy electron diffraction (RHEED) oscillations. Excellent crystallinity was attained in Bi2Se3/α-Al2O3 which exhibited 15 cycles of RHEED oscillations and emerged the Shubnikov-de Haas (SdH) oscillations in transport results. Second, we report excellent crystallinity of c-axis oriented epitaxial TI films Bi2Se3 grown on MI films, a rare-earth iron garnet (ReIG), such as thulium iron garnet (Tm3Fe5O12, TmIG) of perpendicular magnetic anisotropy (PMA) and yttrium iron garnet (Y3Fe5O12, YIG) of in-plane magnetic anisotropy (IMA) by molecular beam epitaxy (MBE) with a Se-buffered low-temperature (SBLT) growth technique. Streaky RHEED patterns starting from the very first quintuple layer (QL) of Bi2Se3 indicated the high-quality interface between ReIGs and Bi2Se3, a requirement for studying interfacial exchange coupling effects. The strong interfacial exchange interaction was manifested by observations of anomalous Hall effect (AHE) in the Bi2Se3/TmIG bilayer and a shift of ferromagnetic resonance field of TmIG and YIG induced by Bi2Se3. To preclude the bulk contribution in TI, the ternary TI (Bi,Sb)2Te3 was fabricated. Two conducting transport channels were revealed form the fitting of Hikami-Larkin-Nagaoka (HLN) equation, indicating the attainment of bulk-insulating feature which was further confirmed by angle-resolved photoemission spectroscopy (ARPES) results. Room-temperature AHE were achieved in the bilayer of (Bi,Sb)2Te3/TmIG through MPE, which is the prerequisite of QAHE in higher temperature. The strong suppression in weak anti-localization with the absence of negative magnetoresistance may be attributed the decoupled surface transport channels in the bulk-insulating films. The work has established the foundations to pay the way to the realization of QAHE by means of MPE.

Abstract i
摘要 iii
Acknowledgement v
Publication list vii
Contents ix
List of figures xii
List of tables xviii
Chapter 1 Introduction 1
1.1 Brief introduction of topological insulators (TIs) 1
1.2 Breaking time-reversal-symmetry by magnetic proximity effect (MPE) 3
1.3 Manipulating the Fermi level (EF) toward the Dirac point: Growth of ternary TI (Bi,Sb)2Te3 6
1.4 Motivation 8
Chapter 2 Instrumentations 10
2.1 Sample growth of TI thin films 10
2.1.1 Molecular beam epitaxy (MBE) 10
2.2 Characterization 12
2.2.1 Reflection high-energy electron diffraction (RHEED) 12
2.2.2 Atomic force microscopy (AFM) 13
2.2.3 transport measurement 13
2.2.4 X-ray diffraction (XRD) 15
2.2.5 X-ray photoemission spectroscopy (XPS) 15
2.2.6 Angle-resolved photoemission spectroscopy (ARPES) 16
2.2.7 Transmission electron microscopy (TEM) 17
2.2.8 Ferromagnetic resonance (FMR) 19
Chapter 3 Growth of binary TI Bi2Se3 thin films on α-Al2O3 and garnet substrates 21
3.1 Overview of the growth of Bi2Se3 21
3.1.1 Progress of our group (what we already did) 21
3.2 α-Al2O3 substrate preparation and characterization 23
3.2.1 Cleaning process 23
3.2.2 Surface morphology 23
3.2.3 Outgassing process in UHV 24
3.3 Bi2Se3 grown on α-Al2O3 26
3.3.1 Growth method: modified two-step growth 26
3.3.2 RHEED patterns and oscillations 27
3.3.3 Surface morphology 35
3.3.4 XRD 39
3.3.5 Transport properties 40
3.3.6 ARPES 45
3.4 Summary (Bi2Se3/α-Al2O3) 46
3.5 Garnet (GGG, YIG, TmIG) substrate preparation and characterization 47
3.5.1 Cleaning process 47
3.5.2 Outgassing process in UHV 47
3.5.3 Surface morphology and other properties 50
3.6 Bi2Se3 grown on YIG and TmIG 51
3.6.1 Growth method: Se-buffered low-temperature (SBLT) growth 51
3.6.2 RHEED patterns 52
3.6.3 Surface morphology 56
3.6.4 Characterization of interface qualities (TEM images and XPS spectra) 58
3.6.5 XRD 60
3.6.6 Bi2Se3/TmIG: transport properties and FMR measurement 61
3.6.7 Bi2Se3/YIG: FMR measurement and spin pumping 66
3.7 Summary (Bi2Se3/YIG or TmIG) 70
Chapter 4 Growth of ternary TI (Bi,Sb)2Te3 thin films on α-Al2O3 and garnet substrates 71
4.1 Overview of the growth of (Bi,Sb)2Te3 71
4.1.1 Progress of our group (what we already did) 71
4.2 (Bi,Sb)2Te3 grown on α-Al2O3 75
4.2.1 RHEED patterns and surface morphology 75
4.2.2 Composition analysis (XRD and XPS) 86
4.2.3 Transport properties 92
4.2.4 ARPES 101
4.3 Summary ((Bi,Sb)2Te3/α-Al2O3) 103
4.4 (Bi,Sb)2Te3 grown on TmIG 104
4.4.1 Growth method: modified low-temperature growth 104
4.4.2 RHEED patterns and surface morphologies 105
4.4.3 Transport properties 111
4.5 Summary ((Bi,Sb)2Te3/TmIG) 120
Chapter 5 conclusion 121
Reference 123

[1] M. Z. Hasan and C. L. Kane, Rev. of Mod. Phys. 82 (4), 3045 (2010).
[2] J. E. Moore, Nature 464, 194 (2010).
[3] X.-L. Qi and S.-C. Zhang, Rev. Mod. Phys. 83 (4), 1057 (2011).
[4] A. P. Schnyder, S. Ryu, A. Furusaki, and A. W. W. Ludwig, Phys. Rev. B 78 (19), 195125 (2008).
[5] D. J. Thouless, M. Kohmoto, M. P. Nightingale, and M. den Nijs, Phys. Rev. Lett. 49 (6), 405 (1982).
[6] M. Kohmoto, Ann. Phys. 160 (2), 343 (1985).
[7] H. Zhang, C.-X. Liu, X.-L. Qi, X. Dai, Z. Fang, and S.-C. Zhang, Nat. Phys. 5 (6), 438 (2009).
[8] S.-Y. Xu, Y. Xia, L. A. Wray, S. Jia, F. Meier, J. H. Dil, J. Osterwalder, B. Slomski, A. Bansil, H. Lin, R. J. Cava, and M. Z. Hasan, Science 332 (6029), 560 (2011).
[9] Y. Ando, J. Phys. Soc. Jpn. 82 (10), 102001 (2013).
[10] C.-Z. Chang and M. Li, Journal of physics. Condensed matter : an Institute of Physics journal 28 (12), 123002 (2016).
[11] A. Roth, C. Brüne, H. Buhmann, L. W. Molenkamp, J. Maciejko, X.-L. Qi, and S.-C. Zhang, Science 325 (5938), 294 (2009).
[12] C.-Z. Chang, W. Zhao, D. Y. Kim, P. Wei, J.  K. Jain, C. Liu, M. H.  W. Chan, and J. S. Moodera, Phys. Rev. Lett. 115 (5), 057206 (2015).
[13] C.-Z. Chang, J. Zhang, X. Feng, J. Shen, Z. Zhang, M. Guo, K. Li, Y. Ou, P. Wei, L.-L. Wang, Z.-Q. Ji, Y. Feng, S. Ji, X. Chen, J. Jia, X. Dai, Z. Fang, S.-C. Zhang, K. He, Y. Wang, L. Lu, X.-C. Ma, and Q.-K. Xue, Science 340 (6129), 167 (2013).
[14] C.-Z. Chang, W. Zhao, D. Y. Kim, H. Zhang, B. A. Assaf, D. Heiman, S.-C. Zhang, C. Liu, M. H. W. Chan, and J. S. Moodera, Nat. Mater. 14, 473 (2015).
[15] M. Liu, J. Zhang, C.-Z. Chang, Z. Zhang, X. Feng, K. Li, K. He, L.-l. Wang, X. Chen, X. Dai, Z. Fang, Q.-K. Xue, X. Ma, and Y. Wang, Phys. Rev. Lett. 108 (3), 036805 (2012).
[16] P. Wei, F. Katmis, B. A. Assaf, H. Steinberg, P. Jarillo-Herrero, D. Heiman, and J. S. Moodera, Phys. Rev. Lett. 110 (18), 186807 (2013).
[17] F. Katmis, V. Lauter, F. S. Nogueira, B. A. Assaf, M. E. Jamer, P. Wei, B. Satpati, J. W. Freeland, I. Eremin, D. Heiman, P. Jarillo-Herrero, and J. S. Moodera, Nature 533, 513 (2016).
[18] Z. Jiang, C.-Z. Chang, C. Tang, J.-G. Zheng, J. S. Moodera, and J. Shi, AIP Adv. 6 (5), 055809 (2016).
[19] H. Wang, J. Kally, J. S. Lee, T. Liu, H. Chang, D. R. Hickey, K. A. Mkhoyan, M. Wu, A. Richardella, and N. Samarth, Phys. Rev. Lett. 117 (7), 076601 (2016).
[20] Y. T. Fanchiang, K. H. M. Chen, C. C. Tseng, C. C. Chen, C. K. Cheng, S. R. Yang, C. N. Wu, S. F. Lee, M. Hong, and J. Kwo, Nat. Commun. 9 (1), 223 (2018).
[21] C. Tang, Q. Song, C.-Z. Chang, Y. Xu, Y. Ohnuma, M. Matsuo, Y. Liu, W. Yuan, Y. Yao, J. S. Moodera, S. Maekawa, W. Han, and J. Shi, Sci. Adv. 4 (6), eaas8660 (2018).
[22] N. Bansal, Y. S. Kim, E. Edrey, M. Brahlek, Y. Horibe, K. Iida, M. Tanimura, G.-H. Li, T. Feng, H.-D. Lee, T. Gustafsson, E. Andrei, and S. Oh, Thin Solid Films 520 (1), 224 (2011).
[23] C. Tang, C.-Z. Chang, G. Zhao, Y. Liu, Z. Jiang, C.-X. Liu, M. R. McCartney, D. J. Smith, T. Chen, J. S. Moodera, and J. Shi, Sci. Adv. 3 (6), e1700307 (2017).
[24] Z. Jiang, C.-Z. Chang, M. R. Masir, C. Tang, Y. Xu, J. S. Moodera, A. H. MacDonald, and Jing Shi, Nat. Commun. 7, 11458 (2016).
[25] C. C. Chen, K. H. M. Chen, Y. T. Fanchiang, C. C. Tseng, S. R. Yang, C. N. Wu, M. X. Guo, C. K. Cheng, S. W. Huang, K. Y. Lin, C. T. Wu, M. Hong, and J. Kwo, Appl. Phys. Lett. 114 (3), 031601 (2019).
[26] J.-M. Zhang, W. Ming, Z. Huang, G.-B. Liu, X. Kou, Y. Fan, K. L. Wang, and Y. Yao, Phys. Rev. B 88 (23), 235131 (2013).
[27] M. Li, Q. Song, W. Zhao, J. A. Garlow, T.-H. Liu, L. Wu, Y. Zhu, J. S. Moodera, M. H. W. Chan, G. Chen, and C.-Z. Chang, Phys. Rev. B 96 (20), 201301 (2017).
[28] H. Steinberg, D. R. Gardner, Y. S. Lee, and P. Jarillo-Herrero, Nano Lett. 10 (12), 5032 (2010).
[29] D. Kong, Y. Chen, J. J. Cha, Q. Zhang, J. G. Analytis, K. Lai, Z. Liu, S. S. Hong, K. J. Koski, S.-K. Mo, Z. Hussain, I. R. Fisher, Z.-X. Shen, and Y. Cui, Nat. Nanotechnol. 6, 705 (2011).
[30] L. He, X. Kou, M. Lang, E. S. Choi, Y. Jiang, T. Nie, W. Jiang, Y. Fan, Y. Wang, F. Xiu, and K. L. Wang, Sci. Rep. 3, 3406 (2013).
[31] J. Zhang, C.-Z. Chang, Z. Zhang, J. Wen, X. Feng, K. Li, M. Liu, K. He, L. Wang, X. Chen, Q.-K. Xue, X. Ma, and Y. Wang, Nat. Commun. 2, 574 (2011).
[32] M. Brahlek, N. Koirala, M. Salehi, N. Bansal, and S. Oh, Phys. Rev. Lett. 113 (2), 026801 (2014).
[33] H. Nakayama, M. Althammer, Y. T. Chen, K. Uchida, Y. Kajiwara, D. Kikuchi, T. Ohtani, S. Geprägs, M. Opel, S. Takahashi, R. Gross, G. E. W. Bauer, S. T. B. Goennenwein, and E. Saitoh, Phys. Rev. Lett. 110 (20), 206601 (2013).
[34] S. Franchi, G. Trevisi, L. Seravalli, and P. Frigeri, Progress in Crystal Growth and Characterization of Materials 47, 166 (2003).
[35] Atenrok, (https://commons.wikimedia.org/w/index.php?curid=27255733).
[36 Yashvant, (https://en.wikibooks.org/wiki/Nanotechnology).
[37] S. Hikami, A. I. Larkin, and Y. Nagaoka, Prog. Theor. Phys. 63 (2), 707 (1980).
[38] Public Domain, (https://en.wikipedia.org/w/index.php?curid=22918777).
[39] (http://d32ogoqmya1dw8.clougfront.net/images/research_education/geochem
sheets/techniques/IUCrimg69.v2.gif).
[40] Bvcrist, (https://zh.wikipedia.org/wiki/File:System2.gif).
[41] Saiht, (https://commons.wikimedia.org/w/index.php?curid=7032316).
[42] Gringer, (https://it.wikipedia.org/wiki/File:Scheme_TEM_en.svg).
[43] Y. Zhang, K. He, C.-Z. Chang, C.-L. Song, L.-L. Wang, X. Chen, J.-F. Jia, Z. Fang, X. Dai, W.-Y. Shan, S.-Q. Shen, Q. Niu, X.-L. Qi, S.-C. Zhang, X.-C. Ma, and Q.-K. Xue, Nat. Phys. 6, 584 (2010).
[44] X. Guo, Z. J. Xu, H. C. Liu, B. Zhao, X. Q. Dai, H. T. He, J. N. Wang, H. J. Liu, W. K. Ho, and M. H. Xie, Appl. Phys. Lett. 102 (15), 151604 (2013).
[45] S.-K. Jerng, K. Joo, Y. Kim, S.-M. Yoon, J. H. Lee, M. Kim, J. S. Kim, E. Yoon, S.-H. Chun, and Y. S. Kim, Nanoscale 5 (21), 10618 (2013).
[46] G. Zhang, H. Qin, J. Teng, J. Guo, Q. Guo, X. Dai, Z. Fang, and K. Wu, Appl. Phys. Lett. 95 (5), 053114 (2009).
[47] Q. Fu, T. Wagner, and M. Rühle, Surf. Sci. 600 (21), 4870 (2006).
[48] S. Y. Lin, Ph. D Thesis (2018).
[49] J. H. Neave, B. A. Joyce, P. J. Dobson, and N. Norton, Appl. Phys. A 31 (1), 1 (1983).
[50] A. Seelig and J. Seelig, Biochemistry 13 (23), 4839 (1974).
[51] C. N. Wu, C. C. Tseng, Y. T. Fanchiang, C. K. Cheng, K. Y. Lin, S. L. Yeh, S. R. Yang, C. T. Wu, T. Liu, M. Wu, M. Hong, and J. Kwo, Sci. Rep. 8 (1), 11087 (2018).
[52] C. N. Wu, C. C. Tseng, K. Y. Lin, C. K. Cheng, S. L. Yeh, Y. T. Fanchiang, M. Hong, and J. Kwo, AIP Adv. 8 (5), 055904 (2018).
[53] J.-Y. Hwang, Y.-M. Kim, K. H. Lee, H. Ohta, and S. W. Kim, Nano Lett. 17 (10), 6140 (2017).
[54] C.-L. Song, Y.-L. Wang, Y.-P. Jiang, Y. Zhang, C.-Z. Chang, L. Wang, K. He, X. Chen, J.-F. Jia, Y. Wang, Z. Fang, X. Dai, X.-C. Xie, X.-L. Qi, S.-C. Zhang, Q.-K. Xue, and X. Ma, Appl. Phys. Lett. 97 (14), 143118 (2010).
[55] K. H. M. Chen, H. Y. Lin, S. R. Yang, C. K. Cheng, X. Q. Zhang, C. M. Cheng, S. F. Lee, C. H. Hsu, Y. H. Lee, M. Hong, and J. Kwo, Appl. Phys. Lett. 111 (8), 083106 (2017).
[56] N. Koirala, M. Brahlek, M. Salehi, L. Wu, J. Dai, J. Waugh, T. Nummy, M.-G. Han, J. Moon, Y. Zhu, D. Dessau, W. Wu, N. P. Armitage, and S. Oh, Nano Lett. 15 (12), 8245 (2015).
[57] A. Quindeau, C. O. Avci, W. Liu, C. Sun, M. Mann, A. S. Tang, M. C. Onbasli, D. Bono, P. M. Voyles, Y. Xu, J. Robinson, G. S. D. Beach, and C. A. Ross, Adv. Electron. Mater. 3 (1), 1600376 (2017).
[58] Z. Jiang, C. Z. Chang, C. Tang, P. Wei, J. S. Moodera, and J. Shi, Nano Lett. 15 (9), 5835 (2015).
[59] Y. Lv, J. Kally, D. Zhang, J. S. Lee, M. Jamali, N. Samarth, and J.-P. Wang, Nat. Commun. 9 (1), 111 (2018).
[60] J. Tang, L.-T. Chang, X. Kou, K. Murata, E. S. Choi, M. Lang, Y. Fan, Y. Jiang, M. Montazeri, W. Jiang, Y. Wang, L. He, and K. L. Wang, Nano Lett. 14 (9), 5423 (2014).
[61] S. R. Yang, Y. T. Fanchiang, C. C. Chen, C. C. Tseng, Y. C. Liu, M. X. Guo, M. Hong, S. F. Lee, and J. Kwo, Phys. Rev. B 100, 045138 (2019).
[62] M. Winnerlein, S. Schreyeck, S. Grauer, S. Rosenberger, K. M. Fijalkowski, C. Gould, K. Brunner, and L. W. Molenkamp, Phys. Rev. Mater. 1 (1), 011201 (2017).
[63] M.  S Dresselhaus, G. Chen, M.  Y Tang, R.  G Yang, H. Lee, D.  Z Wang, Z.  F Ren, J. P. Fleurial, and P. Gogna, Adv. Mater. 19 (8), 1043 (2007).
[64] L. Vegard, Zeitschrift für Physik 5 (1), 17 (1921).
[65] A. R. Denton and N. W. Ashcroft, Phys. Rev. A 43 (6), 3161 (1991).
[66] N. V. Tarakina, S. Schreyeck, M. Luysberg, S. Grauer, C. Schumacher, G. Karczewski, K. Brunner, C. Gould, H. Buhmann, R. E. Dunin-Borkowski, and L. W. Molenkamp, Adv. Mater. Interfaces 1 (5), 1400134 (2014).
[67] B. Skinner, T. Chen, and B. I. Shklovskii, Phys. Rev. Lett. 109 (17), 176801 (2012).