Influence of the Reaction Gases on Graphene Growth on Copper Substrates by Chemical Vapor Deposition
Date Issued
2014
Date
2014
Author(s)
Chang, Ren-Jie
Abstract
Graphene, a two-dimensional hexagonal lattice structure composed of sp2-bonded carbon atoms, has drawn significant attention for its exceptional electrical and mechanical properties. In order to apply graphene in electronic devices, 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, easy control of graphene layer numbers, and, most importantly, its scalability – it has been demonstrated that the size of graphene sheet is large enough for industrial applications. However, the quality of CVD-grown graphene is not comparable with those exfoliated from graphite flakes; the defects, such as the domain boundaries, degrade the carrier mobility in graphene. Therefore, reducing the amount of domain boundaries by means of reducing the nucleation density in the initial stage of graphene growth will be beneficial for improving the electrical properties of graphene-based devices. In this study, we investigate the effects of the reaction gases in CVD graphene growth on the nucleation density. We find that the presence of oxygen prior to graphene growth leads to the formation of copper oxide layers on Cu substrate that passivate the active sites for nucleation, greatly reducing the nucleation density from 104 to 3 nuclei/mm2. Due to the passivation, the graphene domain size increases from 10 μm to 1 mm; the carrier mobility of graphene field effect transistor is increased from 1500 cm2/V s to 3270 cm2/V s, therefore improving the quality of graphene films. When high-reactivity acetylene is used as the carbon source, the growth temperature can be dramatically reduced from 1000℃ to 750℃, making the CVD growth more compatible with the existing semiconductor fabrication processes.
Subjects
石墨烯
化學氣相沉積
成核密度
基板表面氧化層
晶域大小
Type
thesis
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