以兩步驟磊晶硒化鉍薄膜之磁運輸探討

Abstract

近年來，凝聚態物理學和材料科學領域對拓撲絕緣體表現出了極大的興趣，這是因為它們預測的獨特物理性質以及在自旋電子學和量子計算中的潛在應用。拓撲絕緣體是一類材料，其塊材（bulk）帶隙並呈現絕緣體特性，同時在表面存在導電的拓撲表面態，這些表面態由時間反演對稱性所保護。在這項研究中，我們選擇了三維拓樸絕緣體的硒化鉍（Bi2Se3）作為我們的靶材。我們比較了沉積在藍寶石（Al2O3）基板上的Bi2Se3薄膜，其中包含了一步驟爐管磊晶和兩步驟爐管磊晶的薄膜。我們的實驗結果證明，採用兩步驟溫度設定沉積的Bi2Se3薄膜表現出顯著較高的質量。我們對Bi2Se3薄膜進行了全面的分析，包括掃描電子顯微鏡（SEM）、X射線衍射（XRD）和X射線光電子能譜（XPS）。兩步驟溫度磊晶方法在薄膜特性方面取得了優化的結果。經過量測，薄膜厚度通常具有約0.7微米。材料分析揭示了Bi2Se3薄膜的化學鍵合和晶體結構與Bi2Se3單晶體相似。 隨後，我們利用物理特性測量系統（PPMS）對材料薄膜進行磁輸運實驗，探討了拓撲絕緣體的弱反局域效應等特性。通過比較這些薄膜的磁輸運行為，我們對它們對外部磁場的響應和輸運特性有了更深入的了解。我們分析了一步驟磊晶和兩步驟磊晶的薄膜，觀察到兩步驟磊晶的薄膜表現出更明顯的拓撲絕緣體特徵，表現出更顯著的WAL效應、更高的MR值和對外部磁場更大的敏感性。此外，我們觀察到不同的場景，從理想情況（表面貢獻占主導地位）到更現實的情況（大量貢獻占主導地位）。 通過將我們的研究結果與文獻中的數據進行比較，我們能夠揭示Bi2Se3的內在特性，並進一步證實兩步磊晶生長方法相比於一步磊晶過程可以得到質量更高的薄膜。

In recent years, there has been significant interest in topological insulators (TIs) in the fields of condensed matter physics and materials science, driven by their predicted unique physical properties and potential applications in spintronics and quantum computation. TIs are a class of materials characterized by an insulating bulk bandgap and conducting topological surface states (TSS) protected by time-reversal symmetry. In this study, we selected bismuth selenide (Bi2Se3), a three-dimensional topological insulator, as our target material. We compared Bi2Se3 films deposited on sapphire (Al2O3) substrates using one-step furnace heating and two-step furnace heating methods. Our experimental results convincingly demonstrate that Bi2Se3 films deposited with the two-step temperature setting exhibit significantly higher quality. We conducted a comprehensive analysis of the Bi2Se3 films, including scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The two-step temperature deposition process yielded optimized results in terms of film characteristics. Typically, the thin films had a thickness of approximately 0.7 micrometers. Material analysis revealed a strong correlation between the chemical bonding and crystal structure of the Bi2Se3 thin films, resembling those of a single crystal of Bi2Se3. Subsequently, we explored the characteristics of topological insulators, such as the weak antilocalization effect, by conducting magnetotransport experiments on thin films of the material using the Physical Properties Measurement System (PPMS). By comparing the magnetotransport behaviors of these films, we gained a deeper understanding of their response to external magnetic fields and transport properties. We analyzed both one-step and two-step epitaxially grown films and observed that the two-step epitaxial growth demonstrated more pronounced characteristics of a topological insulator, showing a more significant WAL effect, higher MR values, and greater sensitivity to external magnetic fields. Additionally, we observed different scenarios, ranging from the ideal case (with dominant surface contributions) to more realistic situations (where bulk contributions prevail). By comparing our findings with data reported in the literature, we were able to reveal the intrinsic properties of Bi2Se3 and further confirm that the two-step epitaxial growth method results in higher-quality and thin films with better topological characteristics compared to the one-step process.