拓樸絕緣體是一種表面導電內部絕緣的材料，若是加入磁性材料則會破壞時間反演對稱(Time-reversal symmetry)，此時就會形成量子異常霍爾效應，拓樸軸子態這些特殊量子態。MnSb2Te4與Mn(BixSb1-x)2Te4預測為本質性磁性拓樸絕緣體。
本實驗以分子束磊晶系統成長磁性拓樸絕緣體MnSb2Te4、Mn(BixSb1-X)2Te4薄膜，透過調控分壓比以及成長溫度得到晶向結構穩定的MnSb2Te4薄膜，再摻雜Bi元素形成四元磁性拓樸絕緣體，進行物理性質的分析。先以X光繞射儀(X-ray diffraction, XRD)進行晶格結構的分析，確認薄膜以C軸方向成長，透過調控Bi的分壓比觀察樣品結構的變化。藉由X射線光電子能譜儀(X-ray photoelectron spectrometer, XPS)及拉曼光譜儀(Raman spectrometer)確認薄膜的元素和聲子的光學震動模式。利用穿透式電子顯微鏡(Transmission electron microscope, TEM)確認薄膜為層狀結構以及樣品厚度，再使用能量散佈分析儀(Energy dispersive spectrometer, EDS)分析薄膜的化學成分，確認樣品的元素比例。使用原子力顯微鏡(Atomic force microscope, AFM)觀察薄膜表面因為溫度變化而影響薄膜的表面平整度，與觀察不同比例的Bi/Sb摻雜對表面平整度影響。使用角解析光電子能譜(Angle resolved photoemission spectroscopy, ARPES)量測MnSb2Te4與Mn(BixSb1-X)2Te4的能帶結構，由導帶與價帶間的能隙發現表面態存在，證明MnSb2Te4與Mn(BixSb1-X)2Te4皆為拓樸絕緣體，此外透過調控Bi的比例，可達到控制費米能階的位置，並證實MnSb2Te4為p型性質而MnBi2Te4為n型性質，最後利用超導量子干涉儀(Superconducting Quantum Interference Device, SQUID)確認薄膜整體磁性行為。

In this study, MnSb2Te4 and Mn(BixSb1-x)2Te4 magnetic topological insulator thin films were grown on the sapphire(0001) substrate with molecular beam epitaxy(MBE) system. By controlling the growth temperature and flux ratio of Bi and Sb, the high quality and single-phase structure of MnSb2Te4 and Mn(BixSb1-x)2Te4 thin films are performed. Using X-ray diffraction (XRD), the single crystal along c-axis direction in thin films is confirmed and the structure change with adjusting the Bi flux ratio. The elements and the optical vibration modes of thin films are identified by X-ray photoelectron spectrometer (XPS) and Raman spectra. The layered structure and thickness of thin films are characterized with transmission electron microscope (TEM), and chemical composition is analyzed by energy dispersive spectrometer (EDS), which verifies the stoichiometry of thin films. The surface flatness of thin films is affected by the different growth temperature and Bi/Sb flux ratio from the observation of atomic force microscope (AFM). From angle resolved photoemission spectroscopy (AEPES) results, the surface state exist between conduction band and valence band, which certify both MnSb2¬Te4 and Mn (BixSb1-x)2Te4 are topological insulator. Moreover, the band structure of thin films becomes tailored on tuning the ratio of bismuth to antimony so that the variation of Fermi level EF position led to MnSb2Te4 is p-type and Mn (BixSb1-x)2Te4 in n-type properties. The magnetic behavior of the thin films was confirmed with Superconducting quantum interference device (SQUID).

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