Metal catalyzed synthesis of graphene for the preparation of membranes with highest perfection at the atomic scale

• Applicant: Professor Dr. Sebastian Günther
• Subject Area: Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry ; Experimental Condensed Matter Physics
• Term: from 2013 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 242803365

Since the isolation of graphene by micromechanical cleavage this new material has attracted tremendous attention not only because of its unique electronic but also because of its mechanical properties, such as the huge elastic module and intrinsic strength. The exceptional mechanical stability of graphene allows the construction of ultra strong membranes which, when sufficiently reduced in thickness, can be turned into electron transparent windows even for low energy electrons. Since for such an application, graphene flakes of large size and highest crystalline quality are required, we will explore how defect free graphene can be grown via metal catalyzed preparation routes at reasonable growth speed. In particular, we will follow and optimize the graphene growth on Ru(0001) and on Cu substrates (single crystals and polycrystalline foils) using in situ STM, UHV based techniques (LEED, AES and eventually XPS) and in situ LEEM / SPELEEM measurements. Here, especially substrate restructuring effects are addressed as well as the optimization of the CVD process by adding preparation steps that allow the healing of defects present inside the graphene layer.We will further explore lift-off techniques, which will enable us to gently detach the graphene films from the support surface. Here, in situ LEEM studies are planned.The in situ growth experiments on Cu will be combined to our established CVD process for graphene growth, which is performed in a home built reactor and which is run at pressures in in the mbar range. In future experiments we want to tune the CVD process in order to grow large, single crystalline graphene flakes on Cu substrates. For the quality control of the grown graphene films we will apply several additional ex situ techniques (Raman spectroscopy, SEM, ex situ XPS and optical microscopy). We will further study the growth in a combined high pressure - UHV based LEEM study. Finally, the grown graphene will be used to construct electron transparent windows, which will be characterized by Spectroscopic Photoemission and Low Energy Electron Microscopy (SPELEEM) and Scanning Photoelectron Microscopy (SPEM) in synchrotron studies. Due to the close relation of crystalline quality and both, the resulting electronic and mechanical properties, an improved preparation protocol for the formation of defect free graphene will be interesting for other fundamental studies or future graphene based applications.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1459: Graphen
• International Connection: Italy, USA
• Participating Persons: Dr. Luca Gregoratti; Dr. Andrei Kolmakov; Dr. Andrea Locatelli; Dr. Tefvik Onur Mentes