量子材料由於其量子現象相關應用的實現而成為今日的研究新星。拓撲絕緣體(TI) 屬於表現出材料拓撲和非顯然能帶特性的類別之一，直至到今日也引起了廣泛關注和持續研究。
我們能夠簡易理解一拓樸絕緣體薄片為上、下表面態與塊體態，在這樣架構下，電子在擁有類狄拉克能帶結構的類金屬表面態，與類絕緣體的塊體態將會有大相逕庭的行為表現。Xu et al. (Nat. Phys. 10, 956) 裡藉由雙閘極設計的量子霍爾效應量測展示出雙表面態的電子傳輸性質證據。然而，上下表面態各自獨立的量測研究仍在推展中。
於此我們展示了具有上下表面分別金屬接點的四元拓墣絕緣體BiSbTeSe2 ，這些分別的金屬接點對於上下表面水平量測與其之間的垂直量測有者區分其混合訊號至關重要的重要性。
為了實現我們設計的元件模型，我在製程細節上發展了許多方法，其中反應式離子蝕刻由於其對於TI 材料厚度與幾何上的自由度掌控讓我認為是最具前景值得更進一步推展的製程手法。我們藉由如此實驗技術的成果為諸如自旋電晶體和記憶體等不同傳輸機制的元件開啟了嶄新的大道。

Quantum materials become a rising star nowadays due to realizations and applications of quantum phenomena. Topological insulators (TIs) are among one of the categories which behave material topology and nontrivial band properties, giving rise to extensively attention and continuous studies even until today.
It is well understood that a TI film can be regarded as a top, bottom surface states and bulk state. In this case, electrons can behave quite differently in metal-like SS with Dirac-like band structure or in insulator-like BS. Xu et al. (Nat. Phys. 10, 956) demonstrate the transport evidence of both surface state by use of dual gating quantum Hall effect measurement. However, independently detection of top and bottom surface states are yet to be investigated.
Here we demonstrate the quaternary TIs BiSbTeSe2 with both top and bottom metallic contacts that are significant for determining the top-, bot-horizontal and vertical measurement in the same time in order to distinguish the decoupled signals. I developed several kinds of fabrication in order to approaching our model in the devices, where the results indicate that Reactive Ion Etching (RIE) would be the most promising process for its degree of freedom in geometry and thickness of the TI flakes. Our results open avenues for TIs by such experimental technique approaching to different transport mechanics in devices like spin transistors and memories.

1. Novoselov, Kostya S., et al. "Electric field effect in atomically thin carbon films." science 306.5696: 666-669.(2004). Klaus von Klitzing. Physics: 1981-1990 6, 316 (1993).
2. Pizzocchero, Filippo, et al. "The hot pick-up technique for batch assembly of van der Waals heterostructures." Nature communications 7: 11894. (2016).
3. Durand, Corentin, et al. "Differentiation of surface and bulk conductivities in topological insulators via four-probe spectroscopy." Nano letters 16.4: 2213-2220. (2016).
4. von KLITZING, K. L. A. U. S. "The quantized Hall effect." Physics 1981-1990 2: 316. (1993).
5. Bernevig, B. Andrei, Taylor L. Hughes, and Shou-Cheng Zhang. "Quantum spin Hall effect and topological phase transition in HgTe quantum wells." Science 314.5806: 1757-1761. (2006).
6. Chu, Junhao, and Arden Sher. Physics and properties of narrow gap semiconductors. New York: Springer, 2008.Seongshik Oh. Science,. 340: p. 153-154. (6129). (2013).
7. Bernevig, B. Andrei, and Shou-Cheng Zhang. "Quantum spin Hall effect." Physical review letters 96.10: 106802. (2006).
8. Fu, Liang, Charles L. Kane, and Eugene J. Mele. "Topological insulators in three dimensions." Physical review letters 98.10: 106803. (2007).
9. Kane, Charles, and Joel Moore. "Topological insulators." Physics World 24.02 (2011): 32.Haijun Zhang, Chao-Xing Liu, Xiao-Liang Qi, Xi Dai, Zhong Fang, and Shou-Cheng Zhang. Nature Physics 5, 438–442 (2009).
10. Yan, Binghai, et al. "Theoretical prediction of topological insulators in thallium-based III-V-VI2 ternary chalcogenides." EPL (Europhysics Letters) 90.3: 37002. (2010).
11. Miyamoto, K., et al. "Topological surface states with persistent high spin polarization across the Dirac point in Bi 2 Te 2 Se and Bi 2 Se 2 Te." Physical review letters 109.16: 166802. (2012).
12. Miyazawa, Naoki, Masataka Hakamada, and Mamoru Mabuchi. "Antimicrobial
27
mechanisms due to hyperpolarisation induced by nanoporous Au." Scientific reports 8.1: 3870. (2018).
13. Singh, Sourabh, et al. "Linear magnetoresistance and surface to bulk coupling in topological insulator thin films." Journal of Physics: Condensed Matter 29.50: 505601. (2017).
14. Congra,Tulations, Forfin, di ng Theegg, “Commemoration for the promise with the senior YX researching Topological Insulators” Wal of The Future.(2019)
15. Pizzocchero, Filippo, et al. "The hot pick-up technique for batch assembly of van der Waals heterostructures." Nature communications 7: 11894. (2016).
16. Pizzocchero, Filippo, et al. "The hot pick-up technique for batch assembly of van der Waals heterostructures." Nature communications 7: 11894. (2016).
17. Corentin Durand, X.-G. Zhang, Saban M. Hus, Chuanxu Ma, Michael A. McGuire, Yang Xu, Helin Cao, Ireneusz Miotkowski, Yong P. Chen, and An-Ping Li. Nano Lett., 16 (4), pp 2213–2220. (2016).