The practical use of graphene in consumer electronics has not been demonstrated since the size, uniformity, and reliability problems are yet to be solved to satisfy industrial standards. Here we report mass-produced graphene films synthesized by hydrogen-free rapid thermal chemical vapor deposition (RT-CVD), roll-to-roll etching, and transfer methods, which enabled faster and larger production of homogeneous graphene films over 400 × 300 mm(2) area with a sheet resistance of 249 ± 17 Ω/sq without additional doping. The properties of RT-CVD graphene have been carefully characterized by high-resolution transmission electron microscopy, Raman spectroscopy, chemical grain boundary analysis, and various electrical device measurements, showing excellent uniformity and stability. In particular, we found no significant correlation between graphene domain sizes and electrical conductivity, unlike previous theoretical expectations for nanoscale graphene domains. Finally, the actual application of the RT-CVD films to capacitive multitouch devices installed in the most sophisticated mobile phone was demonstrated.

Wetting-transparent graphene films grown in situ by chemical vapor deposition on hydrophobic (roughened) copper surfaces offer excellent resistance to copper corrosion while maintaining the intrinsic hydrophobicity of the surface, enabling superior performance for water-harvesting applications.

Graphene produced by chemical-vapor-deposition inevitably has defects such as grain boundaries, pinholes, wrinkles, and cracks, which are the most significant obstacles for the realization of superior properties of pristine graphene. Despite efforts to reduce these defects during synthesis, significant damages are further induced during integration and operation of flexible and stretchable applications. Therefore, defect healing is required in order to recover the ideal properties of graphene. Here, the electrical and mechanical properties of graphene are healed on the basis of selective electrochemical deposition on graphene defects. By exploiting the high current density on the defects during the electrodeposition, metal ions such as silver and gold can be selectively reduced. The process is universally applicable to conductive and insulating substrates because graphene can serve as a conducting channel of electrons. The physically filled metal on the defects improves the electrical conductivity and mechanical stretchability by means of reducing contact resistance and crack density. The healing of graphene defects is enabled by the solution-based room temperature electrodeposition process, which broadens the use of graphene as an engineering material.

No abstract

Cu etching is one of the key processes to produce large-area graphene through chemical vapor deposition (CVD), which is needed to remove Cu catalysts and transfer graphene onto target substrates for further applications. However, the Cu etching method has been much less studied compared to doping or transfer processes despite its importance in producing higher quality graphene films. The Cu etchant generally includes a strong oxidizing agent that converts metallic Cu to Cu2+ in a short period of time. Sometimes, the highly concentrated Cu2+ causes a side reaction leading to defect formation on graphene, which needs to be suppressed for higher graphene quality. Here we report that the addition of metal-chelating agents such as benzimidazole (BI) to etching solution reduces the reactivity of Cu-etching solution by forming a coordination compound between BI and Cu2+. The resulting graphene film prepared by Cu stabilizing agent exhibits a sheet resistance as lows as ∼200 Ohm/sq without additional doping processes. We also confirmed that such strong doping effect is stable enough to last for more than 10 months under ambient conditions due to the barrier properties of graphene covering the BI dopants, in contrast to the poor stability of graphene additionally doped by strong p-dopant such as HAuCl4. Thus, we expect that this simultaneous doping and etching method would be very useful for simple and high-throughput production of large-area graphene electrodes with enhanced conductivity.