本實驗利用分子束磊晶(Molecular beam epitaxy, MBE)系統成長三維反鐵磁拓撲絕緣體MnBi2Te4薄膜於C軸取向之藍寶石基板(Al2O3[0001])上。利用調控基板的成長溫度與錳(Manganese, Mn)於成長過程中的流量，使Mn進入Bi2Te3的結構中成為全新的化合物MnBi2Te¬4。藉由反射式高能電子繞射儀(Reflection high energy electron diffraction, Rheed)、X光繞射(X-ray diffraction, XRD)與X光電子能譜儀(X-ray Photoelectron Spectroscopy, XPS)的初步分析來製備具有C軸取向的單晶MnBi2Te4，再透過原子力顯微鏡(Atomic force microscope, AFM)與Raman光譜儀(Raman spectrometer)來鑑定薄膜表面的形貌與聲子的光學震動模式，最後透過超導量子干涉儀(Superconducting QUantum Interference Device, SQUID)的量測來確認薄膜整體磁性特性，以及其奈爾溫度的大小(Néel temperature)。量測結果上，我們發現隨著成長溫度的提高，愈有助於Bi2Te3逐漸轉變為MnBi2Te4，且將Mn與Bi的流率比率降低，可以有效解決在製成中副產物碲化錳(MnTe)的產生。

In this experiment, we have demonstrated that the MnBi2Te4 stoichiometric antiferromagnetic topological insulator thin film can be deposited on sapphire substrates by molecular beam epitaxy (MBE) system. We controlled the growth temperature from 320℃ to 430℃ and adjusted the rate of Mn and Bi rate from 0~1 to grow the MnBi2Te4 thin film within the fixed Bi and Te flux ratio. At different growth temperature and the flux ratio of Mn, we synthesized the single crystal MnBi2Te4 thin film to investigate its crystal structure and magnetic properties. The Bi gas partial pressure was fixed at 3×10-8 (torr). Due to the lower flux ratio could affect surface roughness. Then we confirmed preliminary result by in-situ RHEED, which measures that whether the surface was flat or not. The crystal structure, orientation, quality, and film thickness were confirmed by XRD. In optical measurement, E_g^1 、E_g^2 、A_1g^1 、A_1g^2 were observed by Raman spectroscopy. In terms of surface characteristics, there were AFM and SEM, which can observe the surface morphology and confirm the surface roughness. In addition, we confirmed the bonding behavior and quantitative analysis by XPS. Finally, the antiferromagnetic characteristics and its Néel temperature was confirmed by SQUID.

[1] 黃榮俊, "拓樸絕緣體之能帶結構、輸運性質與場效電晶體元件之介紹與研究," 物理雙月刊, vol. 39：5, pp. 39-46, 2017.
[2] B. A. Bernevig, T. L. Hughes, and S.-C. Zhang, "Quantum spin Hall effect and topological phase transition in HgTe quantum wells," science, vol. 314, pp. 1757-1761, 2006.
[3] C. L. Kane and E. J. Mele, "Z 2 topological order and the quantum spin Hall effect," Physical review letters, vol. 95, p. 146802, 2005.
[4] J. C. Teo, L. Fu, and C. Kane, "Surface states and topological invariants in three-dimensional topological insulators: Application to Bi 1− x Sb x," Physical Review B, vol. 78, p. 045426, 2008.
[5] H. Zhang, C.-X. Liu, X.-L. Qi, X. Dai, Z. Fang, and S.-C. Zhang, "Topological insulators in Bi 2 Se 3, Bi 2 Te 3 and Sb 2 Te 3 with a single Dirac cone on the surface," Nature physics, vol. 5, pp. 438-442, 2009.
[6] 張泰榕, "拓樸材料與拓樸能帶理論," 物理雙月刊, vol. 39：5, pp. 21-30, 2017.
[7] X. Kou, M. Lang, Y. Fan, Y. Jiang, T. Nie, J. Zhang, et al., "Interplay between different magnetisms in Cr-doped topological insulators," Acs Nano, vol. 7, pp. 9205-9212, 2013.
[8] C.-Z. Chang and M. Li, "Quantum anomalous Hall effect in time-reversal-symmetry breaking topological insulators," Journal of Physics: Condensed Matter, vol. 28, p. 123002, 2016.
[9] K. He, "The quantum Hall effect gets more practical," Physics, vol. 8, p. 41, 2015.
[10] J. Li, Y. Li, S. Du, Z. Wang, B.-L. Gu, S.-C. Zhang, et al., "Intrinsic magnetic topological insulators in van der Waals layered MnBi2Te4-family materials," Science Advances, vol. 5, p. eaaw5685, 2019.
[11] H. Li, S. Liu, C. Liu, J. Zhang, Y. Xu, R. Yu, et al., "Antiferromagnetic topological insulator MnBi 2 Te 4: synthesis and magnetic properties," Physical Chemistry Chemical Physics, vol. 22, pp. 556-563, 2020.
[12] D. S. Lee, T.-H. Kim, C.-H. Park, C.-Y. Chung, Y. S. Lim, W.-S. Seo, et al., "Crystal structure, properties and nanostructuring of a new layered chalcogenide semiconductor, Bi 2 MnTe 4," CrystEngComm, vol. 15, pp. 5532-5538, 2013.
[13] J. C. A. Huang, "ph. D Thesis," University of Illinois, 1992.
[14] T. Devillers, "Ferromagnetic phases of Ge (1-x) Mn (x) for spintronics applications," Ph. D. thesis, Université Joseph Fourier, Grenoble, 2008.
[15] 杜怡君, 張毓娟, 翁乙壬, 蘇怡帆, 陳世毓, 梁哲銘, et al., "磁性基本特性及磁性材料應用," 國立台灣大學化學系, 1989.
[16] J. B. Goodenough, "Theory of the role of covalence in the perovskite-type manganites [La, M (II)] Mn O 3," Physical Review, vol. 100, p. 564, 1955.
[17] J. Kanamori, "Superexchange interaction and symmetry properties of electron orbitals," Journal of Physics and Chemistry of Solids, vol. 10, pp. 87-98, 1959.
[18] N. A. Spaldin and N. D. Mathur, "Magnetic materials: fundamentals and device applications," PhT, vol. 56, pp. 62-63, 2003.
[19] C. Kettle, "Introduction to Solid State Physics. 6th," ed: New York Wiley.
[20] A. Cho and J. Arthur, "Molecular beam epitaxy, in “Progress in Solid State Chemistry,” volume 10, EHJ McCaldin, editor," ed: Pergamon Press,-New York, 1975.
[21] 董弈, "調控多元鉍化硒合金拓樸絕緣體其電子結構, 傳輸及磁性研究," 成功大學物理學系學位論文, 2007.
[22] 劉昱宏, "利用分子束磊晶成長拓樸絕緣體鉍化硒參雜銻薄膜之特性分析與場效之研究應用," 成功大學物理學系學位論文, 2017.
[23] 張哲華, "厚度對於鉻及銻共摻硒化鉍拓樸絕緣體其磁電性影響之研究," 成功大學物理學系學位論文, 2017.
[24] 王洸富, "屏蔽電荷對 180 度域壁成核動態機制之影響," 成功大學物理學系學位論文, 2010.
[25] C. V. Raman and K. S. Krishnan, "A new type of secondary radiation," Nature, vol. 121, pp. 501-502, 1928.
[26] 張綺芫, "應變調製反尖晶石磁性薄膜的拉曼研究," 成功大學物理學系學位論文, 2017.
[27] 黃振昌, "Surface Analysis lnstrument : X-ray Photoelectron Spectrometer," 國家實驗研究院儀器科技研究中心, pp. 5-6, 1998.
[28] Y.-W. Yang, "BL24A1," NSRRC, 2020.
[29] 劉全璞, "High Resolution Scanning Electron Microscope," 國立成功大學貴重儀器使用中心, 2010.
[30] 陳昭翰, "超導量子干涉元件發展的回顧與展望," 台灣磁性技術協會, vol. 51, pp. 17-25, 2010.
[31] 張烈錚, "Superconducting Quantum Interference Device Vibrating Sample Magnetometer," 國立成功大學貴重儀器使用中心, 2007.
[32] 林宗謀, "磊晶拓樸絕緣體(Sb1-xBix)2Te3之費米能階調控與電性研究," 成功大學物理學系學位論文, 2019.
[33] Y. Chen, L. Xu, J. Li, Y. Li, H. Wang, C. Zhang, et al., "Topological electronic structure and its temperature evolution in antiferromagnetic topological insulator MnBi 2 Te 4," Physical Review X, vol. 9, p. 041040, 2019.
[34] 楊明憲, "透過調控Sb2Te3薄膜厚度觀察雙層異質結構的費米能階改變與其物理特性," 成功大學物理學系學位論文, 2019.
[35] Z. A. Jahangirli, E. H. Alizade, Z. S. Aliev, M. M. Otrokov, N. A. Ismayilova, S. N. Mammadov, et al., "Electronic structure and dielectric function of Mn-Bi-Te layered compounds," Journal of Vacuum Science & Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena, vol. 37, p. 062910, 2019.
[36] A. Ghasemi, D. Kepaptsoglou, A. Figueroa, G. A. Naydenov, P. J. Hasnip, M. I. J. Probert, et al., "Experimental and density functional study of Mn doped Bi2Te3 topological insulator," APL Materials, vol. 4, p. 126103, 2016.
[37] K. Shahil, M. Hossain, D. Teweldebrhan, and A. Balandin, "Crystal symmetry breaking in few-quintuple Bi 2 Te 3 films: Applications in nanometrology of topological insulators," Applied physics letters, vol. 96, p. 153103, 2010.