Line Koefoed,† Mikkel Kongsfelt,† Søren Ulstrup,‡ Antonija Grubišić Čabo,‡ Andrew Cassidy,‡ Patrick Whelan,§ Marco Bianchi,‡ Maciek Spiewanowski,‡ Peter Bøggild,§ Liv Hornekær,‡ Philip Hoffman,‡ Steen U. Pedersen,† Kim Daasbjerg†
†Department of Chemistry and iNANO, Aarhus University, Denmark
‡Department of Physics and Astronomy and iNANO, Aarhus University, Denmark
§Department of Micro and Nanotechnology, Technical University of Denmark, Denmark
Transfer of large single crystal graphene is highly desired and important for applications in nanoelectronics. A promising and inexpensive approach for manufacturing high-quality graphene is chemical vapor deposition (CVD) onto transition metals. In particular, growth of strictly monatomic graphene of well-defined orientation and macroscopic extension can be achieved on metal single crystals such as Ir(111). Unfortunately, the task of transferring such high-quality graphene to other substrates is difficult, because of the strong interaction between the Ir surface and graphene.
In this work we present a new electrochemical method, which in a two-step procedure can accomplish the transfer of high‑quality graphene from Ir(111). First, tetraoctylammonium ions (TOA+) are intercalated between the Ir(111) crystal and graphene by charging the latter. The graphene layer is supported with a drop‑coated polymer layer, before the second electrochemical step is applied. This step consists of electrochemical reduction of protons in aqueous solution to cause hydrogen evolution and, thereby, enabling transfer of large millimeter‑sized and nearly perfect monolayer graphene from Ir to another substrate such as SiO2/Si. After delamination and usual plasma cleaning the crystal may be reused for growing and transferring graphene once again. Raman mapping was used to analyze and determine the structural defects and strained wrinkles in the transferred graphene.
 S. V. Morozov, K. S. Novoselov, M. I. Katsnelson, F. Schedin, D. C. Elias, J. A. Jaszczak, A. K. Geim, Phys. Rev. Lett. 2008, 100, 016602.
 J. Coraux, A. T. N`Diaye, C. Busse, T. Michely, Nano Lett. 2008, 8, 565.
 A. T. N’Diaye, S. Bleikamp, P. J. Feibelman, T. Michely, Phys. Rev. Lett. 2006, 97, 215501.