利用化學氣相沉積法合成石墨烯與其基材效應之研究

石墨烯是由碳原子組成的二維材料，在近年來已經吸引許多材料科學與凝聚態物理的注意以及研究。其中，化學氣相沉積法是最具前景的合成方法，可以降低生產成本，並合成出大面積、高品質的石墨烯。然而，在目前的研究中，石墨烯的成長機制與其基板效應尚未完全的了解。在化學氣相沉積法中，我們利用兩種不同的生長條件來研究石墨烯成長於銅基板上，分別為石墨烯成長與熔融態的銅表面以及介電層材料與固態銅薄膜之介面。論文的第一部分，我們利用銅箔在高溫下合成石墨烯，並結合了電子背向散射繞射與拉曼光譜，以非破壞性的分析技術局部的探測石墨烯的品質與銅基板的晶相。我們觀測到成長石墨烯的銅表面晶相會由兩種成長機制的互相競爭過程而取得最終的結果 (1)石墨烯影響銅表面晶相的重構，並形成以銅(100)取向的晶面出現於表面 (2)由主體再結晶而形成銅(111)面。石墨烯與銅基板的強作用力可以利用氧化亞銅薄膜的插層而減低其效應。研究發現，此氧化亞銅可以弱化石墨烯與銅箔基板的機械吸附力。因此，石墨烯的薄膜可以輕易的分離或者蝕刻並轉移至任何基板，而高單價的銅箔可以再使用成為石墨烯成長的基板。在第二部分，我們成功合成高品質以及晶圓尺寸的石墨烯於絕緣介電層材料上。在這個研究上，我們發現碳原子不只會在銅表面裂解、形成石墨烯，並且會經由銅晶界擴散至銅薄膜與絕緣層的界面。我們利用高解析電子顯微鏡觀測銅薄膜與二氧化矽橫切面有石墨烯的薄膜，作為我們的直接證據。最佳化的參數可以得到連續與大面積的石墨烯薄膜直接成長在介電層材料上。這個方法可以使我們合成出晶圓尺寸的石墨烯在絕緣基板上，並且避免了濕式轉移製程。關鍵字: 石墨烯、銅、化學氣相沉積法、拉曼光譜、電子背向散射繞射、轉印。

關鍵字

石墨烯；銅；化學氣相沉積法；拉曼光譜；電子背向散射繞射；轉印

並列摘要

Graphene is a two dimensional material which attracted a lot of attention in materials science and condensed-matter physic. Chemical vapor deposition (CVD) is the most promising, inexpensive, large-area and readily accessible approach for high quality graphene. However, the growth mechanism between graphene and the substrate is still not well understood. Therefore, we studied two growth conditions for graphene by using copper as substrate, one was graphene grown on melting copper substrate, and the other was solid state copper substrate. In the first part of the thesis, we synthesized graphene on the melting catalyst by using copper foil as substrate in high temperature process. On the other hand, we combine electron backscatter diffraction (EBSD) and Raman mapping as non-destructive characterization techniques to locally probe the interface between graphene and copper foils lattice without removing the graphene. We observed that the crystal structure of the Cu grains under graphene layers is governed by two competing processes: (1) graphene induced Cu surface reconstruction favoring the formation of Cu(100) orientation, and (2) recrystallization from bulk Cu favoring Cu(111) formation. The strong interaction between graphene and Cu could be decoupled by allowing the intercalation of a thin cuprous oxide interfacial-layer. The Cu2O layer is mechanically and chemically weak; hence, graphene films can be detached and transferred to arbitrary substrates and the Cu substrates may be re-used for graphene growth. Secondly, we successfully synthesized a high-quality and wafer scale graphene thin layers on insulating gate dielectrics and studied the graphene growth condition on solid catalyst by using Cu thin film on dielectric substrate. In this work, we report that carbon species dissociated on Cu surfaces not only result in graphene layers on top of the catalytic Cu thin film but also diffuse through Cu grain boundaries to the interface between Cu and underlying dielectrics. The direct evidence for bottom layer graphene at the interface between copper and silicon dioxide was provided by high-magnification TEM in cross section view of the sample. Optimization of the process parameters leads to a continuous and large-area graphene thin layers directly formed on top of the dielectric. This method allows us to achieve wafer-sized graphene on versatile insulating substrates without the need of graphene transfer. Key word: Graphene, Copper, Chemical Vapor Deposition, Raman spectroscopy, Electron backscatter diffraction (EBSD), and Transfer print.

並列關鍵字

Graphene ； Copper ； Chemical Vapor Deposition ； Raman spectroscopy ； Electron backscatter diffraction (EBSD) ； Transfer print

參考文獻

58 Lui, C. H., Liu, L., Mak, K. F., Flynn, G. W. & Heinz, T. F. Ultraflat graphene. Nature 462, 339-341 (2009).

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3 Meyer, J. C. et al. The structure of suspended graphene sheets. Nature 446, 60-63 (2007).

4 Novoselov, K. S. et al. Electric Field Effect in Atomically Thin Carbon Films. Science 306, 666-669 (2004).

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利用化學氣相沉積法合成石墨烯與其基材效應之研究

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