Graphene, a single atomic layer of hexagonally packed carbon atoms, has drawn significant attention with its outstanding electrical, [1] mechanical, [2,3] and chemical properties. [4,5] Various promising applications based on graphene have been demonstrated, such as in electronics, [6,7] optoelectronics, [8,9] and chemical and biological sensing. [10-12] To further envision graphene technology, it is critical to synthesize high-quality graphene on a large scale. Since the first mechanical isolation of graphene from graphite crystal in 2004, [13] intense efforts have been made to develop methods for graphene synthesis, including reduction of graphene oxide, [14] thermal decomposition of SiC, [15,16] and transition metal assisted chemical vapor deposition (CVD) process. [17-22] In particular, graphene synthesized by CVD on Cu [8,10,17] substrates has shown great promise owing to its large size, high quality, and transferability to arbitrary substrates. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.