1429 © 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim wileyonlinelibrary.com small 2012, 8, No. 9, 1429–1435 1. Introduction Graphene is a promising material for electronics due to its unique transport properties such as high carrier mobility, [1,2] quantum Hall effect at room temperature, [3,4] ballistic trans- port, [5–7] and so on. Many studies focused on the methods to obtain graphene. Micromechanically cleaved graphene on silicon dioxide substrate [8,9] is widely used for fundamental research but is less useful for scaled-up applications due to its low yield. Epitaxial growth on silicon carbide (SiC) [10–12] and chemical vapor deposition (CVD) on catalytic metal surfaces by surface precipitation [13,14] or dissociation [15–17] allow scaled-up production of graphene, but these growth approaches are usually carried out at rather high tempera- tures and transfer techniques are usually required when Growth, Characterization, and Properties of Nanographene Wei Yang, Congli He, Lianchang Zhang, Yi Wang, Zhiwen Shi, Meng Cheng, Guibai Xie, Duoming Wang, Rong Yang, Dongxia Shi, and Guangyu Zhang* applying such materials on a nonspecific substrate. To avoid transfer or post-treatment processes, many approaches were developed. For example, Ismach et al. grew graphene on a sacrificial Cu layer [18] which can be evaporated away during synthesis; however, the evaporation of metal films still requires a high-temperature process. Rummeli et al. reported a low-temperature synthesis of nanographene via CVD, [19] but the growth succeeded only on magnesium oxide (MgO). In 2011, we reported the low-temperature (~550 °C) and catalyst-free growth of nanographene films on various substrates by using a remote plasma-enhanced chemical vapor deposition (RPECVD) system. [20] This new growth technique for nanographene is low-cost and compatible with existing semiconductor processing technologies. These nanographene films are optically transparent, mechanically flexible, and electrically conductive with tunable charge-car- rier densities, which indicates great potential in the field of thin-film resistors, electrode materials, and transparent con- ductive films. Moreover, nanographene films have abundant edges, which can be easily functionalized by various chem- ical groups, and thus they are useful for various catalysts or chemical sensors. Here we present a systematic study of nanographene films with focus on their electrical transport properties. Firstly, we review the growth of nanographene films, followed by their DOI: 10.1002/smll.201101827 W. Yang, C. L. He, L. C. Zhang, Y. Wang, Z. W. Shi, M. Cheng, G. B. Xie, D. M. Wang, R. Yang, Prof. D. X. Shi, Prof. G. Y. Zhang Beijing National Laboratory for Condensed Matter Physics and Institute of Physics Chinese Academy of Sciences Beijing 100190, P. R. China E-mail: gyzhang@aphy.iphy.ac.cn A systematic study on nanographene grown directly on silicon dioxide substrates is reported. The growth is carried out in a remote plasma-enhanced chemical vapor deposition system at a low temperature of around 550 °C with methane gas as the carbon source. Atomic force microscopy is used to characterize the nanographene morphology, and Raman spectroscopy, X-ray photoelectron spectroscopy, and scanning tunneling microscopy are exploited to identify the in-plane sp 2 bonding structures of nanographene samples. Electrical transport properties are measured at various temperatures down to 4 K. Tunneling effects, minimal conductance at the charge-neutral point, sheet resistances, and Dirac point position at different channel lengths are investigated. In addition, nanographene film possesses high transmittance properties, as indicated by transmittance spectra. Nanographene devices are fabricated from rippled structures, and show great promise for strain-gauge sensor applications. Nanographene