以脈衝雷射沉積硒化鉍薄膜於藍寶石基板之奈米機械性質研究

Nanoscale Mechanical Characteristics of Bi2Se3 Thin Film Grown on C-plane Sapphire Substrates by Using Pulsed Laser Deposition

賴鴻達(Hong-Da Lai)

指導教授 ： 簡賸瑞

義守大學/理工學院/材料科學與工程學系/博士(2022年)

摘要

本論文以脈衝雷射沉積硒化鉍薄膜(Bi2Se3)於藍寶石基板，並利用X射線繞射(XRD)、原子力顯微鏡(AFM)、掃描式電子顯微鏡(SEM)，以及奈米壓痕儀分析薄膜之微結構、表面形貌與奈米機械性質。
X射線繞射與原子力顯微分析結果顯示：硒化鉍薄膜具有C軸高優選之六方晶體結構與平整的表面特性。奈米壓痕實驗結果：硒化鉍薄膜之硬度及楊氏模數值分別為2.1 ± 0.1 GPa和58.6 ± 4.1 GPa。此外，由奈米壓痕之力位移曲線圖之負載部分觀察到有數個明顯的斷點(pop-ins)行為，這是硒化鉍薄膜因受局部壓痕應力所產生之結構變化特徵，主要的變形機制是差排成核導致滑移帶之形成。進一步以差排理論估算硒化鉍薄膜內由奈米壓痕所致之第一個斷點所生成之差排數量級為10^3，其臨界半徑為5.4奈米。

關鍵字

硒化鉍薄膜 ； 奈米壓痕 ； 硬度 ； 差排

並列摘要

The nanomechanical properties and nanoindentation responses of bismuth selenide (Bi2Se3) thin films are investigated in this study. The Bi2Se3 thin films are deposited on c-plane sapphire substrates using pulsed laser deposition. The microstructural properties and surface features of Bi2Se3 thin films are analyzed by means of X-ray diffraction (XRD) and atomic force micropy (AFM), respectively.
The XRD results indicated that Bi2Se3 thin films are exhibited the hexagonal crystal structure with a c-axis preferred growth orientation. Nanoindentation results showed the hardness and Young’s modulus of Bi2Se3 thin film are obtained 2.1 ± 0.1 GPa and 58.6 ± 4.1 GPa, respectively. In addition, the multiple “pop-ins” displayed in the loading segments of the load-displacement curves, suggesting that the deformation mechanisms in the hexagonal-structured Bi2Se3 films might have been governed by the nucleation and propagation of dislocations. Further, the energetic estimations indicated that the nanoindentation-induced dislocation loops for the first pop-in event is in the order of 10^3 with a critical radius ("r" _c≈ 5.4nm) within Bi2Se3 thin film. Although the estimated dislocation density is relatively low compared to that of polycrystalline films, it is, nevertheless, in line with the scenario of homogeneous dislocation nucleation-induced first “pop-in” event.

並列關鍵字

Bi2Se3 thin films ； nanoindentation ； hardness ； pop-in

參考文獻

[1]Zhang, H.; Liu, C.-X.; Qi, X.-L.; Dai, X.; Fang, Z.; Zhang, S.-C., “Topological insulators in Bi2Se3, Bi2Te3 and Sb2Te3 with a single Dirac cone on the surface.”, Nat. Phys. 2009, 5, 438–442.

[2]Moore, J.E., “The birth of topological insulators.”, Nature 2010, 464, 194–198.

[3]Yazyev, O.V.; Moore, J.E.; Louie, S.G., “Spin Polarization and Transport of Surface States in the Topological Insulators Bi2Se3 and Bi2Te3 from First Principles.”, Phys. Rev. Lett. 2010, 105, 266806.

[4]Min, W.-L.; Betancourt, A.P.; Jiang, P.; Jiang, B., “Bioinspired broadband antireflection coatings on GaSb.”, Appl. Phys. Lett. 2008, 92, 141109.

[5]Qi, X.-L.; Zhang, S.-C., “Topological insulators and superconductors.”, Rev. Mod. Phys. 2011, 83, 1057–1110.