以反應氣氛控制石墨烯成核密度以達大面積石墨烯成長之研究

Increase the domain size of graphene by adjusting the atmosphere in chemical vapor deposition growth

陳友銓(Yu-Chuan Chen)

指導教授 ： 溫政彥

國立臺灣大學/工學院/材料科學與工程學研究所/碩士(2019年)

https://doi.org/10.6342/NTU201903340

摘要

石墨烯為一由含有sp2鍵結的碳原子所組成六角蜂巢狀晶格的二維原子網格，其優異的電子性質，常溫下其電子遷移率超過15000 cm2/V·s，比奈米碳管或矽晶體(monocrystalline silicon)高，及優異的機械性質，是世上最薄卻也是最堅硬的奈米材料，近年來引起許多學者的興趣，也接踵投入研究。如未來要將石墨烯薄膜應用於各式各樣的電子元件上，生產出高品質且穩定的石墨烯薄膜將是至關重要的因素，而在眾多製備石墨烯薄膜的方法當中，利用化學氣相沉積製程進行石墨烯薄膜成長，相較於其他製備方法有著許多優點，其包括好的厚度均勻性和高的純度及密度，除此之外最重要的是化學氣相沉積法能將其製程規模放大，有利於業界進行大面積的生產，以達商業化之目標。
然而，一般化學氣相沈積法在銅箔上成長出的石墨烯，常常是由成核密度極高的數個小核合併成大片薄膜，單一晶粒大小約只有數十微米大小，其不同晶向的晶粒間存在大量晶界，造成電性、機械性質等等的影響，應用在元件中會產生一定的影響。因此，在本論文中，我們探討了化學氣相沉積製程中的反應氣氛對石墨烯薄膜成長的影響，並且在進入石墨烯成長階段之前，先將金屬銅基板置於氧氣氣氛下，使其表面生成穩定的氧化層，有效地鈍化銅金屬表面的成核點，並且調控反應時爐管內的各項參數，使石墨烯在成長初期階段的成核密度可以從104 nuclei/mm2逐步降低至1 nuclei/mm2，建立在此低成核密度的基礎上，並且在成長階段中，儘可能控制條件降低新的成核機會，讓石墨烯單一晶域大小從數十微米達到釐米乃至於公分尺度。

關鍵字

石墨烯 ； 化學氣相沉積 ； 成核密度 ； 晶域大小

並列摘要

Graphene, a two-dimensional hexagonal lattice structure composed of sp2-bonded carbon atoms, surprisingly has outstanding electrical and mechanical properties. These exceptional properties have made graphene a popular material for a decade. On the other hand, the development of liquid cell has attracted significant interest in these years. With finely fabricated liquid cells, it has been possible to image through liquids using TEM with subnanometer resolution, and many previously unseen materials dynamics have been revealed. Recently, the invention of graphene liquid cell provides a better resolution for observing liquid samples in an electron microscope. In order to apply graphene in liquid cell techniques for TEM observation, reliable fabrication methods, which can produce high-quality graphene layers, are very essential. Among the approaches to synthesize graphene, the chemical vapor deposition (CVD) method shows several advantages, including simple fabrication procedures, good step coverage ability, and, most importantly, its scalability – it has been demonstrated that the size of graphene sheet is large enough for many applications.
 To apply graphene in liquid cell, large enough graphene domain size is required. However, graphene synthesized by traditional CVD method is not perfectly suitable for liquid cell application because of small domain size and polycrystalline properties. To enlarge the graphene domain size and acquire single orientation of graphene island, adapted method should be used to conquer these problems. A refined method called oxygen-assisted chemical vapor deposition(OCVD) is introduced. By this way, lower nucleation density and larger graphene domain size can be reached.

並列關鍵字

graphene ； chemical vapor deposition ； nucleation density ； liquid cell

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