摘要
本實驗想要了解鉍化硒/鉍雙原子層這個系統的自旋流轉電流的效率，因為在角解析光電子能譜觀測到Rashba splitting的現象因此期待有很高的轉換效率，以及在自旋幫浦實驗中為了保護表面態而鍍上銅表現出有保護的作用而延伸出銅傳輸層變厚度之實驗。
剛開始在鉍化硒/鉍雙原子層系統與純鉍化硒的自旋幫浦實驗中，純鉍化硒的自旋流轉電流效率遠大於鉍化硒/鉍雙原子層系統，這裡與我們的期待不符合，因此後來利用銅做為自旋流傳輸層來隔絕鐵磁層的磁性保護拓樸表面態，得到的結果翻轉了，鉍化硒/鉍雙原子層系統的自旋流轉電流效率大於純鉍化硒，這結果就符合我們原本預期。
然後在數據中發現銅傳輸層造成電流明顯增益，進而做了銅厚度變化實驗最後在銅傳輸層厚度為7奈米時得到最大的自旋流轉電流效率為2.6奈米。但是增益來源主要是自旋流注入量變少而不是電流變多，這個現象未來還須繼續研究。

關鍵字：自旋幫浦、自旋流轉電流效率、二維電子氣體、鉍化硒

Spin and charge conversion of quantum materials is very popular issue recently. In this thesis, we use topological insulator bismuth selenide and bismuth bilayer and divided three groups to discussion spin-charge conversion individually is Bi2Se3/Bi bilayer versus Bi2Se3 and Bi2Se3/Bi bilayer/Cu(3) versus Bi2Se3/Cu(3) and Bi2Se3/Cu(d=0,3,5,7,9,11) using spin pumping effect.
In first group, we get Bi2Se3/Bi bilayer lower than Bi2Se3. In second group, Bi2Se3/Bi bilayer/Cu(3) higher than Bi2Se3/Cu(3). In third group, we have the optimal spin to charge conversion efficiency when copper is 7nm, Edelstein length, that is very huge, is 2.6nm.

[1] S. M. Huang, A. O. Badrutdinov, L. Serra, T. Kodera, T. Nakaoka, N. Kumagai, Y. Arakawa, D. A. Tayurskii, K. Kono, and K. Ono,“Enhancement of Rashba coupling in vertical In0.05Ga0.95As/GaAs quantum dots”,“Phys. Rev. B 84, 085325 – Published 29 August 2011”

[2] Junsaku Nitta, Tatsushi Akazaki, Hideaki Takayanagi, and Takatomo Enoki , “Gate Control of Spin-Orbit Interaction in an Inverted In0.53Ga0.47As/In0.52Al0.48As Heterostructure”, “Phys. Rev. Lett. 78, 1335 – Published 17 February 1997”

[3] A. Varykhalov, J. Sánchez-Barriga, A. M. Shikin, W. Gudat, W. Eberhardt, and O. Rader. “Quantum Cavity for Spin due to Spin-Orbit Interaction at a Metal Boundary”, “Phys. Rev. Lett. 101, 256601 – Published 17 December 2008”

[4] S. LaShell, B. A. McDougall, and E. Jensen. “Spin Splitting of an Au(111) Surface State Band Observed with Angle Resolved Photoelectron Spectroscopy”, “Phys. Rev. Lett. 77, 3419 – Published 14 October 1996”

[5] Christian R. Ast, Jürgen Henk, Arthur Ernst, Luca Moreschini, Mihaela C. Falub, Daniela Pacilé, Patrick Bruno, Klaus Kern, and Marco Grioni. “Giant Spin Splitting through Surface Alloying”, Phys. Rev. Lett. 98, 186807 – Published 3 May 2007

[6] Yu. M. Koroteev, G. Bihlmayer, J. E. Gayone, E. V. Chulkov, S. Blügel, P. M. Echenique, and Ph. Hofmann., ” Strong Spin-Orbit Splitting on Bi Surfaces”, “Phys. Rev. Lett. 93, 046403 – Published 23 July 2004”

[8] ” Shu Hsuan Su,Pei Yu Chuang,Sheng Wen Chen”, ” Selective Hydrogen Etching Leads to 2D Bi(111) Bilayers on Bi2Se3:Large Rashba Splitting in Topological Insulator Heterostructure”, ” Chem. Mater. 2017, 29, 8992-9000”

[9] J.-C. Rojas-Sánchez, S. Oyarzún, Y. Fu, A. Marty, C. Vergnaud, S. Gambarelli, L. Vila, M. Jamet, Y. Ohtsubo, A. Taleb-Ibrahimi, P. Le Fèvre, F. Bertran, N. Reyren, J.-M. George, and A. Fert, “Spin to Charge Conversion at Room Temperature by Spin Pumping into a New Type of Topological Insulator:α-Sn Films”, “Phys. Rev. Lett. 116, 096602 – Published 1 March 2016”

[10] Saburo Takahashi, Sadamichi Maekawa, “Spin current, spin accumulation and spin Hall effect”, “Published 19 March 2008 • 2008 National Institute for Materials Science”

[11] Axel Hoffmann, “Spin Hall Effects in Metals”, “IEEE TRANSACTIONS ON MAGNETICS, VOL. 49, NO. 10, OCTOBER 2013”

[12] G. Y. Guo, S. Murakami, T.-W. Chen, and N. Nagaosa, “Intrinsic Spin Hall Effect in Platinum: First-Principles Calculations”, “Phys. Rev. Lett. 100, 096401 – Published 3 March 2008”

[13]” E. Lesne1, Yu Fu”, “Highly efficient and tunable spin-to-charge conversion through Rashba coupling at oxide interfaces”, “Nature Materials volume 15, pages 1261–1266 (2016)”

[14]” Mahdi Jamali, Joon Sue Lee”, “Giant Spin Pumping and Inverse Spin Hall Effect in the Presence of Surface and Bulk Spin−Orbit Coupling of Topological Insulator Bi2Se3”, “Nano Lett., 2015, 15 (10), pp 7126–7132”

[15]” S Pinon1,2, D L Diedhiou”, “Development of a microsystem based on a microfluidic network to tune and reconfigure RF circuits”, “Journal of Micromechanics and Microengineering, Volume 22, Number 7”

[16]” J.C. Rojas Sa´nchez, L. Vila”, “Spin-to-charge conversion using Rashba coupling at the interface between non-magnetic materials”, “Nature Communications volume 4, Article number: 2944 (2013)”
[17]” Luqiao Liu, Takahiro Moriyama, D. C. Ralph, and R. A. Buhrman”, “Spin-Torque Ferromagnetic Resonance Induced by the Spin Hall Effect”, “PRL 106, 036601 (2011)”
[18]” O. Mosendz, J. E. Pearson, F.Y. Fradin, G. E.W. Bauer, S. D. Bader, and A. Hoffmann”, “Quantifying Spin Hall Angles from Spin Pumping: Experiments and Theory”, “PRL 104, 046601 (2010)”
[19]” Shuyuan Shi, Aizhu Wang, Yi Wang, Rajagopalan Ramaswamy, Lei Shen, Jisoo Moon, Dapeng Zhu, Jiawei Yu, Seongshik Oh, Yuanping Feng, and Hyunsoo Yang”, “Efficient charge-spin conversion and magnetization switching through the Rashba effect at topological-insulator/Ag interfaces”, “PHYSICAL REVIEW B 97, 041115(R) (2018)”
[20]” Chunhui Du, Hailong Wang, Fengyuan Yang, and P. Chris Hammel”, “Enhancement of Pure Spin Currents in Spin Pumping Y3Fe5O12/Cu/Metal Trilayers through Spin Conductance Matching” ,“PHYSICAL REVIEW APPLIED 1, 044004 (2014)”
[21]” Hailong Wang, James Kally, Joon Sue Lee, Tao Liu, Houchen Chang, Danielle Reifsnyder Hickey,”, “Surface-State-Dominated Spin-Charge Current Conversion in Topological-Insulator–Ferromagnetic-Insulator Heterostructures”, “PRL 117, 076601 (2016)”