Will graphene be the material of the 21st century?
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h as Si. Mechanically, it is the strongest material ever measured. It has the highest thermal conductivity at 10 times higher than copper. Among the unusual and interesting characteristics of graphene, one should mention that electrons move with zero mass and constant velocity in graphene, just like photons, with diffusion lengths reaching the micrometer regime. In addition, graphene is also an excellent light absorber, which is a very useful characteristic in photonics. For their research work on exfoliated graphene, Geim and Novoselov were awarded the 2010 Physics Nobel Prize while, at the same time, for investigating and developing graphene grown epitaxially on wide-bandgap SiC substrates, de Heer received the 2010 MRS Medal. Graphene research and development has exploded in many major institutions around the world, as showcased in this expanded MRS Bulletin issue on graphene. With graphene in hand as a “novel” semiconductor, three issues need to be addressed: (1) growing high-quality, large-area wafers; (2) functionalization of the material; and (3) envisioning possible new advanced applications. While new approaches are still being discovered and developed, high-quality graphene is now available in various forms, due to the very significant progress in the field of material growth. To develop and implement successful and practical technological applications, the next mandatory step is graphene functionalization. This includes (1) bandgap monitoring, since graphene is a zero bandgap semiconductor, (2) doping, (3) metal-graphene interface control to achieve high-quality ohmic contacts, (4) graphene-substrate interface control and passivation, and (5) graphene nano-ribbon engineering. All of these require good control of the graphene surface and interface, as well as advanced nanotechnologies. While all of these steps are being investigated intensively, achieving significant progress, the most challenging one is certainly to obtain a high-quality metal-graphene ohmic contact, since graphene is just a single atomic layer of carbon atoms. Achieving successful graphene functionalization opens new prospects in many advanced applications in electronics, sensors, photonics, including infrared/THz and lasers, touchscreen technology, micro- and nanoelectromechanical systems (MEMS and NEMS), metrology, and spintronics, with devices potentially having unsurpassed characteristics. In addition, graphene as a carbon-based material is biocompatible and could be very useful in interfacing with biology. New classes of graphene-based sensors are under development. Graphene is also promising for spintronics, initiated by the discovery in the late 1980s of the giant magnetoresistance effect by Fert and Grünberg, who consequently were awarded the 2007 Nobel Prize in Physics. Another extremely interesting and unique aspect of graphene was demonstrated very recently. The spin diffusion lengths in epitaxial graphene were found to exceed 100 μm, paving the road for large-scale spin-based logic circuits beyond CMOS. One can argue that no o
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