在本實驗中，主要利用MBE在sapphire基板上成長Sb2Se3-Bi2Se3拓樸與一般絕緣體多層系統，優化最上層Bi2Se3使其為拓樸的形貌，並探討其物理特性。
藉由不同製程成長三層系統和多層系統，從AFM觀察最上層Bi2Se3形貌變化，發現會由正交晶系(orthorhombic)變成菱形晶系(rhombohedral)，同時也利用XPS分析，說明最上層Bi2Se3沒有Sb原子摻雜。
我們進一步從電性上探討整體傳輸性質，從Rs量測下，表面皆為拓樸形貌的系統電阻值明顯比單層Bi2Se3低，整體傳輸像是並聯概念，再由PPMS量測發現α值由-0.53上升到-0.96，說明在介面處有多一個通道(channel)，其結果也和Rs相符合。
最後由ARPES分析，表面電子能帶結構明顯有表面態(surface state)存在，再由TEM觀察整體系統的橫截面(cross section)，明顯是由Bi2Se3和Sb2Se3組成。

In this research,We use MBE to grow the topological insulator and ordinary insulator Sb2Se3-Bi2Se3 multiple layer system on the sapphire substrate.We optimize the system to make the top Bi2Se3 become the topological morphology and discuss its physical properties.
The trilayer system and multiple layer system are grown by different fabrication to observe the transformation of the top Bi2Se3’s suface morphology by atomic force microscopy (AFM). It shows that the top Bi2Se3’s suface morphology changes from orthorhombic to rhombohedral.The nonexistence of Sb atom on the top Bi2Se3 is confirmed by X-ray photoelectron spectroscopy (XPS).
We further explore the overall transport properties.From 4-wire measurement,the resistance of the improved system is lower than that of single layer Bi2Se3 because its overall transport is like a parallel circuit.Next,we can get the relation between MRs and B from PPMS measurement.we obtain |α| by fitting relation with HLN equation It apparently rises from 0.53 to 0.96,indicating that there is one more channel at the interface and the result is also consistent with Rs.
Topological surface state of the improved system is comfimed by angle resolved photoemission spectroscopy (ARPES),and then the cross section is obviously composed of Bi2Se3 and Sb2Se3 by Transmission electron microscopy (TEM).Our results demonstrate we grow Sb2Se3-Bi2Se3 multiple layer system and the top Bi2Se3 remains topological characteristics.

[1] 鍾亞宸, "利用MBE成長Sb2Se3-Bi2Se3 異質結構並探討其特性," 物理學系, 成功大學, 2016年, 2016.
[2] J. E. Moore, "The birth of topological insulators," Nature, vol. 464, p. 194, 03/10/online 2010.
[3] X.-L. Qi and S.-C. Zhang, "Topological insulators and superconductors," Reviews of Modern Physics, vol. 83, no. 4, pp. 1057-1110, 10/14/ 2011.
[4] G. E. Moore, "Cramming more components onto integrated circuits," Proceedings of the IEEE, vol. 86, no. 1, pp. 82-85, 1998.
[5] J. Moore, "Topological insulators: The next generation," Nature Physics, vol. 5, no. 6, p. 378, 2009.
[6] X.-L. Qi and S.-C. Zhang, "The quantum spin Hall effect and topological insulators," arXiv preprint arXiv:1001.1602, 2010.
[7] C. L. Kane and E. J. Mele, "Quantum spin Hall effect in graphene," Physical review letters, vol. 95, no. 22, p. 226801, 2005.
[8] K. v. Klitzing, G. Dorda, and M. Pepper, "New Method for High-Accuracy Determination of the Fine-Structure Constant Based on Quantized Hall Resistance," Physical Review Letters, vol. 45, no. 6, pp. 494-497, 08/11/ 1980.
[9] B. A. Bernevig and S.-C. Zhang, "Quantum Spin Hall Effect," Physical Review Letters, vol. 96, no. 10, p. 106802, 03/14/ 2006.
[10] C. L. Kane and E. J. Mele, "Z2 Topological Order and the Quantum Spin Hall Effect," Physical Review Letters, vol. 95, no. 14, p. 146802, 09/28/ 2005.
[11] J. E. Moore and L. Balents, "Topological invariants of time-reversal-invariant band structures," Physical Review B, vol. 75, no. 12, p. 121306, 03/26/ 2007.
[12] 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, no. 5806, p. 1757, 2006.
[13] M. Z. Hasan and C. L. Kane, "Colloquium: Topological insulators," Reviews of Modern Physics, vol. 82, no. 4, pp. 3045-3067, 11/08/ 2010.
[14] D. Hsieh et al., "A tunable topological insulator in the spin helical Dirac transport regime," Nature, vol. 460, p. 1101, 07/20/online 2009.
[15] C. Jozwiak et al., "Widespread spin polarization effects in photoemission from topological insulators," Physical Review B, vol. 84, no. 16, p. 165113, 10/14/ 2011.
[16] J. G. Checkelsky, Y. S. Hor, R. J. Cava, and N. P. Ong, "Bulk Band Gap and Surface State Conduction Observed in Voltage-Tuned Crystals of the Topological Insulator Bi2Se3," Physical Review Letters, vol. 106, no. 19, p. 196801, 05/10/ 2011.
[17] J. Chen et al., "Gate-Voltage Control of Chemical Potential and Weak Antilocalization in Bi2Se3," Physical Review Letters, vol. 105, no. 17, p. 176602, 10/19/ 2010.
[18] Y. S. Kim et al., "Thickness-dependent bulk properties and weak antilocalization effect in topological insulator Bi2Se3," Physical Review B, vol. 84, no. 7, p. 073109, 08/26/ 2011.
[19] J. Tian et al., "Quantum and Classical Magnetoresistance in Ambipolar Topological Insulator Transistors with Gate-tunable Bulk and Surface Conduction," Scientific Reports, Article vol. 4, p. 4859, 05/07/online 2014.
[20] Z. H. Wang et al., "Granularity Controlled Nonsaturating Linear Magnetoresistance in Topological Insulator Bi2Te3 Films," Nano Letters, vol. 14, no. 11, pp. 6510-6514, 2014/11/12 2014.
[21] W. Zhang, R. Yu, H.-J. Zhang, X. Dai, and Z. Fang, "First-principles studies of the three-dimensional strong topological insulators Bi2Te3, Bi2Se3and Sb2Te3," New Journal of Physics, vol. 12, no. 6, p. 065013, 2010/06/17 2010.
[22] M. J. Brahlek et al., "Tunable inverse topological heterostructure utilizing (Bi1-xInx)2Se3," Physical Review B, vol. 93, no. 12, p. 125416, 03/10/ 2016.
[23] M. Brahlek et al., "Topological-Metal to Band-Insulator Transition in (Bi1-xInx)2Se3," Physical Review Letters, vol. 109, no. 18, p. 186403, 10/31/ 2012.
[24] Z. Hurych, D. Davis, D. Buczek, C. Wood, G. J. Lapeyre, and A. D. Baer, "Photoemission studies of crystalline and amorphous Sb2Se3," Physical Review B, vol. 9, no. 10, pp. 4392-4404, 05/15/ 1974.
[25] S. D. Shutov, V. V. Sobolev, Y. V. Popov, and S. N. Shestatskii, "Polarization Effects in the Reflectivity Spectra of Orthorhombic Crystals Sb2S3 and Sb2Se3," physica status solidi (b), vol. 31, no. 1, pp. K23-K27, 1969.
[26] N. S. Platakis and H. C. Gatos, "Threshold and memory switching in crystalline chalcogenide materials," physica status solidi (a), vol. 13, no. 1, pp. K1-K4, 1972.
[27] H. Zhang, C.-X. Liu, X.-L. Qi, X. Dai, Z. Fang, and S.-C. Zhang, "Topological insulators in Bi2Se3, Bi2Te3 and Sb2Te3 with a single Dirac cone on the surface," Nature Physics, Article vol. 5, p. 438, 05/10/online 2009.
[28] L. R. Gilbert, B. Van Pelt, and C. Wood, "The thermal activation energy of crystalline Sb2Se3," Journal of Physics and Chemistry of Solids, vol. 35, no. 12, pp. 1629-1632, 1974/01/01/ 1974.
[29] R. Vadapoo, S. Krishnan, H. Yilmaz, and C. Marin, "Electronic structure of antimony selenide (Sb2Se3) from GW calculations," physica status solidi (b), vol. 248, no. 3, pp. 700-705, 2011.
[30] Q. Zhang, Z. Zhang, Z. Zhu, U. Schwingenschlögl, and Y. Cui, "Exotic Topological Insulator States and Topological Phase Transitions in Sb2Se3–Bi2Se3 Heterostructures," ACS nano, vol. 6, no. 3, pp. 2345-2352, 2012.
[31] 林明昱, "Sb2Te3參雜Se之磊晶結構與特性研究。國立成功大學物理學系碩士論文," 物理學系, 成功大學, 2015年
2015.
[32] 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," 物理學系, 成功大學, 2017年, 2017.
[33] 鄧至翔, "變溫成長BiTeSe合金之研究," 物理學系, 成功大學, 2015年, 2015.
[34] 紀淵程, "雙層鉍與碲化鉍異質界面之製備以及物理特性之研究," 物理學系, 成功大學, 2017年, 2017.
[35] 國立成功大學貴重儀器使用中心. (2015). 物理性質量測系統儀 PPMS [Online]. Available: http://ctrmost.web2.ncku.edu.tw/p/404-1054-7410.php?Lang=zh-tw.
[36] 國立成功大學貴重儀器使用中心. (2010). 高解析分析電子顯微鏡 HR-AEM [Online]. Available: http://ctrmost.web2.ncku.edu.tw/p/405-1054-7290,c2083.php?Lang=zh-tw.
[37] Y. Zhao et al., "Demonstration of surface transport in a hybrid Bi2Se3/Bi2Te3 heterostructure," Scientific Reports, Article vol. 3, p. 3060, 10/28/online 2013.
[38] N. Koirala et al., "Record Surface State Mobility and Quantum Hall Effect in Topological Insulator Thin Films via Interface Engineering," Nano Letters, vol. 15, no. 12, pp. 8245-8249, 2015/12/09 2015.
[39] M. A. Tumelero, L. C. Benetti, E. Isoppo, R. Faccio, G. Zangari, and A. A. Pasa, "Electrodeposition and ab Initio Studies of Metastable Orthorhombic Bi2Se3: A Novel Semiconductor with Bandgap for Photovoltaic Applications," The Journal of Physical Chemistry C, vol. 120, no. 22, pp. 11797-11806, 2016/06/09 2016.