Synthesis of high-quality monolayer and bilayer graphene on copper using chemical vapor deposition

The mechanisms determining the growth of high-quality monolayer and bilayer graphene on Cu using chemical vapor deposition (CVD) were investigated. It is shown that graphene growth on Cu is not only determined by the process parameters during growth, but also substantially influenced by the quality of Cu substrate and how the Cu substrate is pretreated. It is found that the micro-topography of the Cu surface strongly affects the uniformity of grown graphene while the purity of the Cu film determines the number of synthesized graphene layers at low pressure conditions. On the other hand, a minimum partial pressure of hydrocarbon is required for graphene to cover the Cu surface during graphene growth. The optimized bilayer graphene exhibits a maximum hole (electron) mobility of 5500 cm(2)V(-1)s(-1)(3900 cm(2)V(-1)s(-1)). A new growth mode resulting in tetragonal shaped graphene domain, which is different from the known lobe structure (for monolayer) or hexagonal (for few layer) mode, is also discovered under our experimental conditions. Furthermore, high resolution transmission electron microscopy has revealed the non-ideal nature of CVD graphene structure for the first time, indicating an important cause of electron/hole mobility degradation that is typically observed in CVD graphene. This observation could be crucial for optimization of the CVD process to further improve the quality of graphene. (C) 2011 Elsevier Ltd. All rights reserved.