An anisotropic etching effect in the graphene basal plane.

Figure 1 . Anisotropic etching of graphite by H 2 -plasma. a–c) AFM images of pristine, 50 W plasma-etched, and 100 W plasma-etched graphite. Plasma etching was performed at 500 ° C for 2 h. Magnifi ed images for the marked areas are shown. d) Measured maximum etching rate of graphite at various etching temperatures. The plasma power was 100 W. Solid lines represent Lorentzian line shape fi ts. e) Average etching speeds for graphite at different etching time intervals. The etching temperature was 500 ° C. Graphene shows great potential for future electronics due to its extraordinary electrical properties and structure-engineerable nature. [ 1–3 ] Control of the edge structure of graphene is crucial during the fabrication process because the electrical, magnetic, and electrochemical properties of graphene are dependent on it, especially in quantum-confi ned graphene structures. [ 4–18 ] Electron-beam lithography and isotropic plasma etching are usually used for patterning graphene nanostructures. However, it is diffi cult to identify the crystallographic orientation and achieve smooth graphene edges simultaneously during fabrication, and one must therefore contend with graphene nanostructures with unknown crystallographic orientation and irregular edges. [ 4 , 5 ] Anisotropic etching has been proposed as a key technique for controllable graphene edge fabrication with atomic precision. So far, anisotropic etching of graphene has been realized by either catalytic nanoparticle cutting [ 19–22 ] or selective reaction of oxidized graphene with a SiO 2 substrate, [ 23 ] but it is diffi cult to apply such methods to a practical fabrication process because they are either substrate-limited or the cutting position, direction, and speed are not controllable. In this paper, we report a dry, anisotropic etching method for graphite and graphene. We are able to control the etching from the edges by tuning etching parameters such as plasma intensity, temperature, and duration. The etching process is attributed to hydrogenation and volatilization of carbon atoms and the etching dynamics are consistent with methane formation. This simple, clean, controllable, and scalable technique is compatible with existing semiconductor processing technology. Anisotropic etching was fi rst applied to graphite because it consists of stacked graphene layers. The graphite samples