Publication

1. Controlled oxidative functionalization of monolayer graphene by water-vapor plasma etching SF1 Group 刘磊、吴慕鸿、杨晓霞、王文龙*、许智、白雪冬* Tel: 82649248; E-mail: wwl@iphy.ac.cn; xdbai@iphy.ac.cn Abstract We present studies on the controlled step-by-step oxidative functionalization of monolayer graphene by chemically reactive water-vapor plasma dry etching. The use of a porous mask on top of the graphene sheets as a filter is essential to reduce the density of free radicals and weaken the sputtering effect. Micro-Raman spectroscopy, X-ray photoelectron spectroscopy and atomic force microscopy showed that the oxidation occurred in a mild and controllable way, and that a wide variety of oxygen-containing functional groups can be evenly and incrementally incorporated onto the carbon lattice. By monitoring the electrical property changes in the graphene at different levels of oxidation, we observed a transformation of the electrical conduction process from continuum percolation to variable range hopping and/or electric-field-driven tunneling, due to the progressive increase of sp3-based basal plane distortion that disrupts the transport of carriers delocalized in the sp2 carbon network. c Fig. 1 (a) Schematic illustration showing the milder water vapor plasma etching of graphene, with the use of a porous mask to filter the reactive free radicals. (b, c) SEM images of the monolayer graphene devices after plasma treatment without (b) and with (c) mask. Red dashed box in (b) indicates the original graphene topography before plasma treatment. Fig. 2 Raman spectra of the monolayer graphene sheets (mechanically cleaved) with various plasma treatment durations. Fig. 4 (a) Typical AFM image of monolayer graphene after exposure to plasma for 3 min. (b) Zoom-in AFM image. (c) Histogram of the height distribution for pristine graphene (green squares), graphene for plasma etching time of 3 min (red circles) and 6min (blue triangles). Fig. 3 (a) C1s XPS spectrum of CVD-grown monolayer graphene after water-vapor plasma treatment (100W, 5min). (b) The atomic ratio of C/O of graphene as a function of plasma treatment time. Fig. 5 (a) Schematic device layout and (b) SEM image of a window-type graphene electrical device. The length of window size is 2.5 lm. (c) Gate dependence of the source–drain current (Ids). (d) Conductance of device as a function of the exposure durations. Publication Lei Liu, Donglin Xie, Muhong Wu, Xiaoxia Yang, Zhi Xu, Wenlong Wang*, Xuedong Bai, and Enge Wang, “Controlled oxidative functionalization of monolayer graphene by water-vapor plasma etching”, Carbon, 2012, 50, 3039-3044. SF1组联系人: 白雪冬，Tel: 82648032; E-mail: xdbai@iphy.ac.cn