Triggering the Continuous Growth of Graphene Toward Millimeter-Sized Grains

• Published in: Advanced functional materials 2013-01, Vol.23 (2), p.198-203
• Main Authors: Wu, Tianru, Ding, Guqiao, Shen, Honglie, Wang, Haomin, Sun, Lei, Jiang, Da, Xie, Xiaoming, Jiang, Mianheng
• Format: Article
• Language: English
• Subjects: Carbon; Chemical vapor deposition; continuous growth; Density; Grains; Graphene; millimeter-sized graphene; Nucleation; nucleation control; Nuclei; polystyrene; Single crystals; solid carbon sources
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.201201577

A simple but efficient strategy to synthesize millimeter‐sized graphene single crystal grains by regulating the supply of reactants in the chemical vapor deposition (CVD) process is demonstrated. Polystyrene is used as a carbon source. Pulse heating on the carbon source is utilized to minimize the nucleation density of graphene on copper foil, while a gradual increase in the temperature of the carbon source and the flow rate of hydrogen is adapted to drive the continuous growth of the graphene grains. As a result, the nucleation density of graphene grain can be controlled to as low as ≈100 nuclei/cm2, and a single crystal grain can grow up to dimensions of ≈1.2 mm. Raman spectroscopy, transmission electron microscopy (TEM), and electrical‐transport measurements show that the graphene grains obtained are of high quality. The strategy presented provides very good controllability and enables the possibility of large graphene single crystals, which is of vital importance for practical applications. The key to synthesizing large graphene grains by ambient pressure chemical vapor deposition (APCVD) is to maintain a low nucleation rate and to provide a continuous drive for graphene growth. An optimized process enables ≈100 nuclei/cm2 on a finely polished and annealed substrate. A continuous increase in carbon supply and flow rate drives the graphene growth to ≈1.2 mm, the largest reported on a Cu substrate.