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10 Large Scale Graphene by Chemical Vapor Deposition: Synthesis, Characterization and Applications 1. Introduction Lewis Gomez De Arco, Yi Zhang and Chongwu Zhou University of Southern California USA Faster and smaller computers, smarter medicaments, ultrasensitive sensors, dreams of a new generation of products that are increasingly cleaner, lighter, stronger and more efficient; those are aspects that represent the aspirations of a great part of human kind that ever more strives for better technologies. Interestingly, the concept of nanotechnology is at the center of this discussion. Nanotechnology has become instrumental on finding pathways to arrive to processes and products that are not only needed today but will become essential in the future. Nanotechnology can be defined as the understanding and manipulation of matter with at least one dimension of the order of 1 to 100 nanometers, where unique phenomena enable novel applications. For example, whereas elemental carbon is a poor conductor of electricity and not particularly strong, the two-dimensional carbon is a semimetal that exhibits high charge carrier mobility, obeying the laws of relativistic rather than regular quantum mechanics. Furthermore, one-dimensional carbon has mechanical strength 100 times higher than steel, exhibiting either metallic or semiconducting properties depending on their chiral atomic arrangement. Two principal factors cause nanomaterials properties to differ significantly from bulk materials: increased relative surface area, which can change or enhance chemical reactivity (Arenz, Mayrhofer et al. 2005); and quantum effects that can affect the material optical, magnetic and electrical properties (Yu, Li et al. 2003). It is precisely the collection of new and surprising properties of nanomaterials what has motivated the scientific and engineering community to invest a tremendous share of effort towards a better understanding of their physical and chemical properties; as well as finding controllable synthesis and accurate characterization techniques. Graphene sheets are one-atom thick, 2D layers of sp2-bonded carbon. It is interesting that carbon with sp2 hybridization is able to form the two-dimensional graphene, the planar local structure in the closed polyhedral of the fullerene family and the cylinder-shaped carbon nanotubes, all with different physical properties (see table 1). Thus, keeping the sp2 hybridization, the 2D carbon can be wrapped up into 0D fullerenes, rolled into 1D nanotubes, or stacked into 3D graphite. Carbon has four electrons in its valence level with a configuration of 2s22p2. The hexagonal structure of graphene poses an alternate double bond arrangement that makes it perfectly conjugated in sp2 hybridization. In this case its px and py orbitals contain one electron each, and the remaining pz has only one electron. This pz orbital overlaps with the pz orbital of aPDF Image | GRAPHENE SYNTHESIS CHARACTERIZATION PROPERTIES
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