本篇論文主要探討三種不同的拓樸材料，分別是成長於銻化銦(001)面上的α錫(灰錫)以及成長於藍寶石基板上的硒化鉍以及銻碲化鉍，本文第一部分將介紹拓樸材料α錫的電子傳輸性質，而第二部分則是硒化鉍以及銻碲化鉍的場效應研究。
α錫是一種半金屬材料，藉由將α錫成長於銻化銦基板後，些許的晶格不匹配所產生的壓縮應變，使得α錫成為一種拓樸材料，然而目前為止，並沒有相關的研究，是從電性上探討成長於銻化銦基板的α錫的拓樸性質，因此我們利用分子束磊晶技術(molecular beam epitaxy, MBE)先在銻化銦(001)面基板上成長銻化銦磊晶層，再將十個或者是三十個雙原子層厚度的α錫成長於銻化銦磊晶層上，在經過X光繞射鑑定確定成長的錫為α相後，我們在物理性質量測系統(PPMS)中進行α錫的傳輸性質量測，清楚的Shubnikov-de Haas (SdH)震盪在低溫高磁場下被觀察到，在萃取出SdH震盪的最大值以及最小值後可將Landau-level fan diagram繪製出來，並且我們進一步分析出SdH震盪的Berry phase為 π，這樣的結果顯示SdH震盪可能來自狄拉克費米子(Dirac fermion)，接下來，我們施加對樣品不同方向的磁場進行SdH震盪的量測，藉此我們可以知道貢獻SdH震盪的費米面(Fermi surface)為三維，這樣的結果代表成長於銻化銦磊晶層及銻化銦(001)面基板的十個雙原子層厚度α錫可能是三維的拓樸狄拉克半金屬(three-dimensional topological Dirac semimetal)。
在場效應的研究中，我們利用場效應調控拓樸絕緣體硒化鉍以及銻碲化鉍的費米能階(Fermi level)，雖然拓樸絕緣體的表面態(topological surface state)擁有許多有趣的傳輸特性，像是電子的自旋與動量的方向維持一定的方向關係(spin-momentum locking)，且電子不會受到背向散射所影響，使得硒化鉍以及銻碲化鉍成為一個具有潛力應用在超低功耗自旋電子學原件的材料，然而由於高密度的缺陷影響，硒化鉍的費米能階位於導帶中，使得表面態對傳輸的貢獻減少，因此，藉由將高介電係數的氧化層沉積在硒化鉍以及銻碲化鉍並製成頂閘極結構，我們計畫利用場效應將硒化鉍的費米能階調控至塊材能隙之中，並將銻碲化鉍的載子從n型調控制p型，但為了保護硒化鉍以及銻碲化鉍的表面態不受到沉積氧化物時的影響，我們使用分子束磊晶以及原子層沉積(atomic layer deposition, ALD)的方式，成長不同種類的氧化物於硒化鉍進行比較，本篇研究我們選用了四種不同的氧化層結構，分別為ALD-Al2O3 、 ALD-Al2O3 / MBE-Al2O3 、 ALD-Al2O3 / MBE-Y2O3、 ALD-Al2O3 / oxidized MBE-Al；並藉由X射線光電子能譜(X-ray photoelectron spectroscopy, XPS)探討氧化層與硒化鉍的界面反應，我們發現MBE-Y2O3和ALD-Al2O3與硒化鉍之間的界面，幾乎沒有化學反應的訊號被觀察到，並且藉由量測漏電流密度與電場的特性(leakage current density-electric field characteristics)，我們發現藉由沉積一層MBE-Al2O3或是MBE-Y2O3在硒化鉍與ALD-Al2O3之間，可以有效地增加閘極可施加的偏壓，最後，我們將ALD-Al2O3沉積與硒化鉍上並利用黃光微影技術製成頂閘極原件以進行場效應研究，藉由從0施加至15伏特的偏壓，我們發現硒化鉍的載子濃度總共下降約2.0×10E13 cm^-2。

In this study, three topological materials, α-Sn on InSb(001), Bi2Se3 and (Bi1-xSbx)2Te3, will be discussed here. The first section is the electrical transport study of α-Sn, and the next section is the electrical field effect study of Bi2Se3 and (Bi1-xSbx)2Te3.
Unstrain α-Sn is a trivial semimetal. By depositing α-Sn on InSb substrate, the lattice mismatch between α-Sn and InSb induced a compressive strain and this compressive strain let α-Sn change into a topologically nontrivial material. Nowadays, there is still not any transports measurement, which was done for identifying the topological properties of α-Sn on InSb. In our study, the high quality 10 and 30 bilayer (BL) α-Sn was grew on the InSb epilayer (epi-InSb) / InSb(001) substrate. The phase of α-Sn was identified by X-ray diffraction. Then, the transport properties of the α-Sn thin films were measured by physical property measurement system (PPMS). The clear Shubnikov-de Haas (SdH) oscillations were observed in low temperature and high magnetic field. By plotting the positions of maxima and minima of the SdH oscillation, the Landau-level fan diagram was constructed to extract the Berry phase and the oscillation frequency. Then, the Berry phase π was obtained from the Landau-level fan diagram. It suggests that the SdH oscillation comes from Dirac fermion. Moreover, by taking the dependence of the SdH oscillation on the angle θ between the magnetic field direction and the surface normal, we can identify that the SdH oscillation comes from three-dimension (3D) Fermi surface. This results suggest that both of 10 BL and 30BL α-Sn on epi-InSb / InSb(001) substrate are 3D topological Dirac semimetal (TDS).
In the electrical field effect study, the electrical field effect was utilized to control the Fermi level (EF) of TI, Bi2Se3 and (Bi1-xSbx)2Te3. Although the topological surface state (TSS) displays a wide variety of interesting transport properties such as spin-momentum locking and the absence of backscattering, which are promising for spintronics, yet the bulk contribution due to the high density of defects in Bi2Se3 overwhelms the surface contribution. Therefore, the electrical field effect was utilized to tune the EF of Bi2Se3 toward bulk energy gap and control the EF of (Bi1-xSbx)2Te3 from the top of Dirac point to the bottom of Dirac point. We proposed to fabricate the top gate structure by depositing high- dielectric layer on Bi2Se3 and (Bi1-xSbx)2Te3. To protect the top surface of Bi2Se3 and (Bi1-xSbx)2Te3, we compared various kinds of high-κ dielectric stacks deposited on Bi2Se3 by molecular beam epitaxy (MBE) and atomic layer deposition (ALD). Four different dielectric stacks were choose to deposit on Bi2Se3, such as ALD-Al2O3, ALD-Al2O3 / MBE-Al2O3, ALD-Al2O3 / MBE-Y2O3 and ALD-Al2O3 / oxidized MBE-Al. To analyze the top surface of Bi2Se3, in-situ XPS was utilized to analyze the chemical reaction between dielectric layer and Bi2Se3. The leakage current density-electric field (J-E) and capacity-voltage (C-V) characteristics of different dielectric stacks were also measured. The results show that by inserting MBE-Al2O3 or MBE-Y2O3 between ALD-Al2O3 and Bi2Se3, higher gate bias can be applied than that of ALD-Al2O3 deposited on Bi2Se3 directly. Last, the sample of ALD-Al2O3 on Bi2Se3 was fabricated into a top-gating device using photolithography. By gating from 0 to -15 V, the total reduction of charge carriers (ΔN2D) is ~2.0×10E13 cm^-2.

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