| 摘要: | 在這篇論文中，我們一揭鹼金屬鹵化物輔助熱化學氣相沉積的面紗，全面了解單層二硫化鎢和雙層二硫化鎢的成長機制。在考慮了系統邊界條件、氣體流速、成長基板形貌與性質、成長溫度、各種前驅物的蒸氣壓與加熱溫度後，我們在同一個系統中呈現了幾乎現有研究中所有二硫化鎢的形式。我們發現其中最重要的參數是成長基板形貌與性質、成長溫度、以及各項前驅物的蒸氣壓，而其他的參數其實都是改變前述三個重要參數的手法。一系列的對照實驗論證了這些參數如何影響晶粒大小、晶粒形狀、晶粒密度。我們除了用自動化程式觀察、分析並量化了這些整體的成長，我們還研究了二硫化鎢從單層成長到密實雙層的成長動力學。這篇論文致力於了解二硫化鎢的成長細節以及引導大家成長出任何型態的二硫化鎢。各個領域的研究者或業者只要在自己的系統中成長出可見的二硫化鎢晶粒後，不論目標是三角形或六角形的單層、密實或樹突狀的雙層、小於10微米或是大於200微米，都可以經由參照我們的地圖，成功且輕易地合成各式的晶粒。在應用方面，我們開發出了一種不需要光阻的製程—散射離子摻雜。藉由控制單層二硫化鎢的缺陷型態以及缺陷密度，我們既得以避免任何殘留物物又可以局部調控其能帶結構。除了以光學性質的改變間接佐證其電子結構的調變外，更進一步從實驗上與理論上研究其摻雜的機制。;A full picture of the growth mechanism of WS2 monolayers and bilayers through alkali-metal-halide-assisted thermal chemical vapor deposition (t-CVD) was unveiled in all aspects. Almost all types of WS2 flakes were demonstrated in the same system and considered almost all of the factors which may influence the synthesis, including the geometry of the system boundaries, the flow rate, the morphology and the properties of the growth substrate, the growth temperature, the vapor pressure, and the heating temperature of each precursor. We found that, among all parameters, the most important factors are the growth temperature, the vapor pressure, and the heating temperature of each precursor. Other parameters are just ways to alter these three main factors. A series of experiments were carried out and showed how these factors affect grain size, grain shape, and grain density. Moreover, not only the overall growth process was observed, analyzed, and quantified by an automatic program, but the grain evolution from a monolayer to a compact bilayer was also studied. This thesis provides detailed studies on the growth mechanism of WS2 and is a guide for the synthesis of any type of WS2. Once you get the first observable result in your system, no matter whether it is triangular or truncated monolayers, compact or concentric bilayers, flakes smaller than 10 µm or flakes larger than 200 µm, you can easily achieve successful synthesis by following the map in this thesis. Moreover, we developed a method for lithography without any photoresist, which is called “selective ion implantation.” The electronic structure of WS2 monolayers is manipulated through good control of defect type and defect density without any residues. We verified the achievement through optical measurements and further revealed the mechanism of their doping effect experimentally and theoretically. |
