藉由分子束磊晶(MBE)，成功將碲化鉍、碲化銻拓樸絕緣體薄膜成長在藍寶石基板上，由臨場高能量電子繞射儀(RHEED)及原子力顯微鏡(AFM)顯示這些表面平滑的薄膜，再經由X光繞射(XRD)看出碲化鉍、碲化銻薄膜為單晶結構。底定出碲化鉍最佳的合金結構品質的成長條件為：鉍碲比例為1:10且成長溫度在310 ℃；而碲化銻的最佳成長條件為：銻碲比例為1:17且成長溫度在275 ℃。最後藉由角解析光電子能譜(ARPES)，觀察到碲化鉍、碲化銻薄膜的表面態，直接證實其為拓樸絕緣體。
在獲得碲化鉍、碲化銻單層薄膜的成長參數後，成長變厚度的碲化銻/碲化鉍雙層膜於藍寶石基板上，再將其做成元件，量測載子傳輸的特性。最後於固定底層碲化鉍厚度且改變上層碲化銻厚度的實驗中，觀察到載子傳輸行為的改變。相信藉由此種調控雙層拓樸絕緣體厚度的方法，能在將來提供給相關領域的學者參考與使用。

Bi2Te3 and Sb2Te3 topological insulator thin films have been successfully grown on Al2O3 (0001) substrates by molecular beam epitaxy (MBE). In-situ reflection high energy electron diffraction (RHEED) and ex-situ atomic force microscopy (AFM) indicate the smooth surface of the thin films. Single crystalline structure of both Bi2Te3 and Sb2Te3 films are presented in XRD spectra. The optimal growth condition for Bi2Te3 (Sb2Te3) is that the substrate nominally set at 310 ℃ (275 ℃) with beam flux ratio Bi:Te ~ 1:10 (Sb:Te ~ 1:17). At last, the surface state of Bi2Te3 and Sb2Te3 thin films via ARPES reveals that they are indeed topological insulators.
After obtaining the growth conditions of Bi2Te3 and Sb2Te3 single layer, we fabricated Sb2Te3/ Bi2Te3 bilayer on Al2O3 (0001) substrates and transferred a Hall bar pattern onto the films by photolithography. Electrical transport properties illustrate the transition of carrier transport behavior with varying the thickness of Sb2Te3 upper layer. We can assert that such method of regulating the thickness of bilayer topological insulator to tune the Dirac point to a desired energetic position will play an important role in the near future.

[1] Bernevig, B.A., T.L. Hughes, and S.-C. Zhang, Quantum spin Hall effect and topological phase transition in HgTe quantum wells. Science, 2006. 314(5806): p. 1757-1761.
[2] Hsieh, D., et al., Observation of time-reversal-protected single-Dirac-cone topological-insulator states in Bi2Te3 and Sb2Te3. Physical review letters, 2009. 103(14): p. 146401.
[3] Xia, Y., et al., Observation of a large-gap topological-insulator class with a single Dirac cone on the surface. Nature physics, 2009. 5(6): p. 398.
[4] Hasan, M.Z. and C.L. Kane, Colloquium: topological insulators. Reviews of Modern Physics, 2010. 82(4): p. 3045.
[5] He, L., X. Kou, and K.L. Wang, Review of 3D topological insulator thin‐film growth by molecular beam epitaxy and potential applications. physica status solidi (RRL)–Rapid Research Letters, 2013. 7(1‐2): p. 50-63.
[6] Kong, D. and Y. Cui, Opportunities in chemistry and materials science for topological insulators and their nanostructures. Nature Chemistry, 2011. 3(11): p. 845.
[7] Moore, J.E., The birth of topological insulators. Nature, 2010. 464(7286): p. 194.
[8] Qi, X.-L. and S.-C. Zhang, Topological insulators and superconductors. Reviews of Modern Physics, 2011. 83(4): p. 1057.
[9] Qi, X.-L. and S.-C. Zhang, The quantum spin Hall effect and topological insulators. arXiv preprint arXiv:1001.1602, 2010.
[10] Chen, Y., et al., Experimental realization of a three-dimensional topological insulator, Bi2Te3. science, 2009. 325(5937): p. 178-181.
[11] Kane, C.L. and E.J. Mele, Quantum spin Hall effect in graphene. Physical review letters, 2005. 95(22): p. 226801.
[12] Moore, J.E. and L. Balents, Topological invariants of time-reversal-invariant band structures. Physical Review B, 2007. 75(12): p. 121306.
[13] König, M., et al., Quantum spin Hall insulator state in HgTe quantum wells. Science, 2007. 318(5851): p. 766-770.
[14] Hsieh, D., et al., A tunable topological insulator in the spin helical Dirac transport regime. Nature, 2009. 460(7259): p. 1101.
[15] Jozwiak, C., et al., Widespread spin polarization effects in photoemission from topological insulators. Physical Review B, 2011. 84(16): p. 165113.
[16] Ando, Y., Topological insulator materials. Journal of the Physical Society of Japan, 2013. 82(10): p. 102001.
[17] Cao, Y., et al., Syntheses and thermoelectric properties of Bi2Te3/Sb2Te3 bulk nanocomposites with laminated nanostructure. Applied Physics Letters, 2008. 92(14): p. 143106.
[18] Mishra, S., S. Satpathy, and O. Jepsen, Electronic structure and thermoelectric properties of bismuth telluride and bismuth selenide. Journal of Physics: Condensed Matter, 1997. 9(2): p. 461.
[19] Thonhauser, T., et al., Thermoelectric properties of Sb2Te3 under pressure and uniaxial stress. Physical Review B, 2003. 68(8): p. 085201.
[20] Xiao, Z., et al., Fabrication of Bi2Te3/Sb2Te3 and Bi2Te3/Bi2Te2Se multilayered thin film-based integrated cooling devices. Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 2010. 28(4): p. 679-683.
[21] Zhang, X., et al., Investigation on the electrical transport properties of highly (00l)-textured Sb2Te3 films deposited by molecular beam epitaxy. Journal of Applied Physics, 2014. 115(2): p. 024307.
[22] Takashiri, M., et al., Role of stirring assist during solvothermal synthesis for preparing single-crystal bismuth telluride hexagonal nanoplates. Materials Chemistry and Physics, 2016. 173: p. 213-218.
[23] Wang, G., et al., Atomically smooth ultrathin films of topological insulator Sb2Te3. Nano Research, 2010. 3(12): p. 874-880.
[24] Chen, X., et al., Molecular beam epitaxial growth of topological insulators. Advanced Materials, 2011. 23(9): p. 1162-1165.
[25] Zhang, H., et al., Topological insulators in Bi2Se3, Bi2Te3 and Sb2Te3 with a single Dirac cone on the surface. Nature physics, 2009. 5(6): p. 438.
[26] Harrison, S., et al., Two-step growth of high quality Bi2Te3 thin films on Al2O3 (0001) by molecular beam epitaxy. Applied Physics Letters, 2013. 102(17): p. 171906.
[27] Eschbach, M., et al., Realization of a vertical topological p-n junction in epitaxial Sb2Te3/Bi2Te3 heterostructures. Nat Commun, 2015. 6: p. 8816.
[28] Herman, M.A. and H. Sitter, Molecular beam epitaxy: fundamentals and current status. Vol. 7. 2012: Springer Science & Business Media.
[29] Huang, J.-C., Studies of nucleation, coherent tilt and surface phase transitions by molecular beam epitaxy. 1992, University of Illinois at Urbana-Champaign.
[30] 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. 2017.
[31] Wilson, R.A. and H.A. Bullen, Introduction to Scanning Probe Microscopy (SPM): Basic Theory Atomic Force Microscopy (AFM). Creative Commons Attribution-Noncommercial-Share Alike, 2006. 2.
[32] 陳品卉, 單晶碲化鉍/硒化鉍拓樸絕緣體多層膜之磊晶成長及結構研究. 2013.
[33] Hall, E.H., On a new action of the magnet on electric currents. American Journal of Mathematics, 1879. 2(3): p. 287-292.
[34] Hall, E.H., XVIII. On the “Rotational Coefficient” in nickel and cobalt. The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science, 1881. 12(74): p. 157-172.
[35] Brune, H., Growth Modes. 2001, Pergamon.
[36] Chambers, S.A., Epitaxial growth and properties of thin film oxides. Surface science reports, 2000. 39(5-6): p. 105-180.
[37] Chien, Y.-J., Z. Zhou, and C. Uher, Growth and transport properties of Sb2− xVxTe3 thin films on sapphire substrates. Journal of crystal growth, 2005. 283(3-4): p. 309-314.
[38] Wang, G., et al., Topological insulator thin films of Bi2Te3 with controlled electronic structure. Advanced Materials, 2011. 23(26): p. 2929-2932.
[39] Eschbach, M., et al., Realization of a vertical topological p–n junction in epitaxial Sb2Te3/Bi2Te3 heterostructures. Nature communications, 2015. 6: p. 8816.
[40] Pradyumnan, P., Thermoelectric properties of Bi2Te3 and Sb2Te3 and its bilayer thin films. 2010.
[41] Sze, S.M. and K.K. Ng, Physics of semiconductor devices. 2006: John wiley & sons.
[42] Li, Y.Y., et al., Intrinsic topological insulator Bi2Te3 thin films on Si and their thickness limit. Advanced materials, 2010. 22(36): p. 4002-4007.
[43] Wang, W., et al., Epitaxial growth and characterization of high-quality aluminum films on sapphire substrates by molecular beam epitaxy. CrystEngComm, 2014. 16(33): p. 7626-7632.
[44] Raposo, M., Q. Ferreira, and P. Ribeiro, A guide for atomic force microscopy analysis of soft-condensed matter. Modern research and educational topics in microscopy, 2007. 1: p. 758-769.
[45] Feutelais, Y., et al., A study of the phases in the bismuth-tellurium system. Materials research bulletin, 1993. 28(6): p. 591-596.
[46] Liu, W.K. and M.B. Santos, Thin films: heteroepitaxial systems. Vol. 15. 1999: World Scientific.
[47] 陳奕帆, 磊晶鉍化碲的微結構與電性隨成長溫度之研究. 2014.
[48] Plucinski, L., et al., Robust surface electronic properties of topological insulators: Bi2Te3 films grown by molecular beam epitaxy. Applied physics letters, 2011. 98(22): p. 222503.
[49] Peranio, N., et al., Room temperature MBE deposition of Bi2Te3 and Sb2Te3 thin films with low charge carrier densities. physica status solidi (a), 2012. 209(2): p. 289-293.