CleanGRAPH

The scientific and technological interest in Graphene has recently exploded due to its unique properties, promising many exciting applications in optics, mechanics and electronics. However many challenges remain before graphene can be integrated into sophisticated devices. The electronic states of graphene are strongly affected by surface charges, and the presence of surface contaminants dramatically degrades the film properties, especially the electronic mobility. Therefore, a key point in all graphene-based technology is the development of cleaning techniques, which can selectively etch surface contaminants. However, no such technology exists at present. For nano-electronic applications the opening of an electronic band gap is another challenge. This could be achieved either by substitutional doping or by edge patterning of graphene nano-ribbons, but mo mature processes have been developed. This project will address these issues by developing innovative plasma processes. Plasma surface processing is universally used for integrated circuit fabrication. However, plasma processing of graphene remains marginal, with only a few papers published in 2012. This is mainly because conventional plasma sources are too aggressive for atomically thin layers, usually causing damage the basal plane of graphene. However, we will investigate the use of novel low ion energy plasma sources which have recently been developed for the microelectronic and photovoltaic industries to reduce plasma induced damage and allow controlled atomic-scale etching. The goal of this project is to evaluate two new plasma sources (Pulsed ICP plasmas at LTM and TVWP at LPP/LPICM) to clean, dope and pattern graphene layers in a controlled way, opening the possibility for graphene device manufacturing. These plasma sources have demonstrated remarkable capabilities in 2012 to etch and deposit ultrathin layers. In particular, H2 plasmas are promising for graphene cleaning (H atoms can etch amorphous hydrocarbons while preserving the integrity of the graphene), while Cl2, N2 and BCl3 are interesting for graphene doping. Efficient process development will be achieved using the following strategy: 1) Molecular Dynamic simulations (MD) to predict the necessary flux and energy of particles to the surface; 2) Plasma diagnostics to control the flux and energy of incident particles; 3) Surface diagnostics to monitor the effect of the plasma treatment. Several powerful surface analysis techniques (XPS, Raman, XPEEM, µ-Auger) will be used to characterize the effect of plasma treatment on the film structure, composition and electronic properties. Finally, we plan to fabricate and electrically characterize real electronic devices in graphene. Our success will repose upon the complementary skills of the five partners in graphene devices, in plasma processing and in surface characterization. I-Néel has expertise in the CVD growth of high mobility graphene on large area substrates and the fabrication and electrical characterization of graphene electronic devices. LTM, LPP and LPICM are specialized in the characterization and development of plasma processes for microelectronic and photovoltaic applications, respectively. They have recently developed the two new plasma sources at the heart of this project. Finally, CEA-LETI has the expertise in photoelectron spectromicroscopy (XPEEM) combined with scanning probes and Auger microscopies. XPEEM provides direct, spatially-resolved information on the surface chemical properties and band structure of graphene relevant to doping and cleaning (Dirac point and Fermi level positions). This tool will guide the development of plasma cleaning, doping and etching of graphene. Thanks to our complementary expertise, we aim to achieve technological breakthroughs in the fabrication of graphene devices, which will be of great utility to the entire national graphene community