摘要
　　拓樸絕緣體，內部為絕緣體，而在邊緣或表面的自旋電子卻有導電。其中之一，過渡金屬二硫族化合物(TMDs)其能隙很大，這種特性對電晶體是很重要的。近年來，因此近年來，這類型的材料受到科學家們的重視。
　　本研究使用掃描穿隧式電子顯微鏡觀察二硒化鎢/雙層石墨稀樣品經過加熱表面形貌變化，樣品製作過程為：6H-碳化矽(0001)上先製備雙層石墨稀，並以雙層石墨稀當基底以分子磊晶法成長二硒化鎢單層以及雙層結構，藉此探討二硒化鎢/雙層石墨稀隨不同熱退火過程、以不同探針偏壓下觀察二硒化鎢表面變化。
　　實驗中主要探討三個方面，分別是：一、二硒化鎢/雙層石墨稀其不同偏壓下二硒化鎢的表面電荷密度變化，此性質與理論預測有關聯，二維材料的過渡金屬二硫族化合物其1T’結構具有拓樸絕緣體邊緣態性質，因此我們希望觀察二硒化鎢在雙層石墨稀上的是否有其邊緣態特性。二、在熱退熱至不同溫度時，二硒化鎢表面結構、面積分布的變化。三、探討二硒化鎢在邊緣狀態的內部物理探討。在第一方面，我們在部分二硒化鎢島嶼觀察到隨著不同偏壓，表現出在島嶼邊緣狀態電子雲密度較島嶼內部來的高，我們稱其為Type B；在另一部分的二硒化鎢並不會有隨著偏壓改變而有急劇的電子密度差異，我們稱為Type A。第二方面，我們觀察到Type A在熱退火超過380℃即消失，而Type B依舊存在，且配合角解析光電子能譜儀數據，因此我們推論Type A應為1T’結構，Type B為1H結構。第三方面，我們推論在二硒化鎢島嶼內部會隨著偏壓改變的二硒化鎢Type B(1H)，應當與在二硒化鎢大能隙範圍內，探針取得相同穿隧電流值必須更靠近樣品，才高度隨偏壓改變的性質，另外在邊緣不隨偏壓改變高度的特性為：二維材料在邊緣有因無法形成共價鍵的電子所造成，並非拓樸邊緣態造成。
　　雖然我們對於1T’結構的性質探討，並沒有成功證明其拓樸絕緣的性質，然而，本篇論文中探討了過程中表面發生的各種現象如：二硒化鎢1T’與1H隨偏壓改變的性質，隨溫度改變的二硒化鎢表面，1H結構邊緣態的推論等，這些成果將提供給未來研究過渡金屬二硫化物的學者們有用的幫助。

Abstract
　　The topological insulators are insulating in their bulk, and at the edge or surface of the spin electrons have conductive characterizations. Meanwhile, two-dimensional (2D) transition metal dichalcogenides (TMDs) MX2 (M = Mo, W; X = S, Se) semiconductors have been important materials of the transistor due to their sizable energy bandgaps. Those materials are popular for scientist.
　　In this study, the surface morphology of the WSe2/bilayer graphene sample was observed by using scanning tunneling microscope upon annealing at various temperatures. The bilayer-graphene is prepared by heating 6H-Silicon-Carbia at 1300℃ several times. The WSe2 film is formed by co-deposition of W and Se on the bilayer-graphene surface by molecular beam epitaxy. The evolution of the surface structure of the WSe2 film was explored by changing the annealing temperatures and STM bias.
　　The experiment mainly discusses three aspects. First, the surface charge density of WSe2 on bilayer graphene is probed at different biases. Theoretical studies predicted that the TMDs with 1T' structure are 2D topological insulators. Thus, we are interested in whether the WSe2 film exhibits the properties of 2D topological insulators. Second, how the surface of the WSe2 film changes upon heating to elevated temperatures. Thirdly, if the edge state exists on the WSe2 film or not. In the first aspect we observed in some the WSe2 islands with different bias voltages. The electron cloud density at the edge of some islands was higher than that in the islands; these are called Type B. Some other parts of the the WSe2 film does not have a sharp difference in electron density as the bias voltage changes; these are called Type A. In the second aspect, we observe that Type A disappears at a temperature of higher than380 ° C, but type B remains. By comparing with the ARPES data, we believe that Type A should have 1T ' structure and Type B has the 1H structure. In the third aspect, we suggest that the large band gap lead to the type B changes with the different bias at the terrace; in other hand, we also suggest that the electron of boundary type B can not be make of covalent bond, which the electron cloud density is higher than that in the island.
　　Although our results reveal the nature of the 1T ' structure, and did not succeed in proving its topological insulation property. However, we explore the various phenomena that occur on the surface during annealing processes. For example, 1T 'and 1H structure of tungsten diselenide with the nature of the bias change, 1H structure of the edge of the inference. These results will shine light to the further understanding of transition metal dichalcogenides.

目錄
第一章 簡介 1
1.1 研究動機 1
1.2 碳化矽晶體結構與石墨稀晶面 2
1.3 拓樸絕緣體 4
1.4 相關文獻 7
1.4.1過渡金屬二硫族化物維拓樸絕緣體預測 7
1.4.2單層1T’結構二鍗化鎢在雙層石墨稀上的二維拓樸絕緣體 9
1.4.3二硒化鉬/銀(111)的1H邊緣結構研究 11
第二章 儀器工作原理 14
2.1 真空系統與實驗儀器 14
2.1.1真空系統 14
2.1.2真空幫浦及氣壓測量儀介紹 14
2.1.3抽真空概略程序 19
2.2 掃描穿隧顯微鏡 21
2.2.1 量子穿隧效應 21
2.2.2 掃描穿隧式電子顯微鏡細部構造 23
2.2.3 掃描穿隧式顯微鏡成像原理 25
2.3蒸鍍槍原理 26
2.4 探針製作與樣品準備 27
2.4.1 探針製作 27
2.4.2 雙層石墨稀/碳化矽(0001)準備及二硒化鎢的製備資訊 29
2.4.3 熱電偶基本原理與量測 30
第三章 實驗結果與討論 32
3.1 二硒化鎢在熱退火至230℃清除表面硒原子的表面形貌 32
3.2 將二硒化鎢/雙層石墨稀熱退火至300℃的表面形貌 33
3.3加熱至340℃與360℃二硒化鎢/雙層石墨稀的表面形貌 37
3.3.1 熱退火二硒化鎢/雙層石墨稀至340℃表面形貌 37
3.3.2 熱退火至360℃表面形貌 39
3.4 加熱至380℃二硒化鎢/雙層石墨稀的表面形貌 41
3.5 加熱至400℃至440℃二硒化鎢/雙層石墨稀的表面形貌 43
3.6 其他討論 46
3.6.1 二硒化鎢第二層與第一層高度隨偏壓的關係 46
3.6.2 二硒化鎢/雙層石墨稀的表面隨溫度變化之面積分布與推論 49
3.6.3 二硒化鎢Type B(H結構)島嶼內部與邊緣討論 51
第四章 結論 55
參考文獻 57

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