Fabrication of lithographic and self-organized graphene ribbons grown on SiC

It has been shown that the edge properties play an important role in transport in narrow ribbons. In this work, we prepare two types of graphene ribbons within a few hundred nm by vastly different fabrication techniques to discuss the edge effects. The first type of samples is made by electron-beam lithography and conventional RIE etching processes. Strong negative magnetoresistance (MR) behavior is observed due to the consequence of disorder in the edge structure (e.g. chemical dopants, the resolution of e-beam lithography and so on). The second type of ribbons on SiC is self-organized, and grown “naturally” (i.e., similar to the way large-area monolayer graphene can be prepared by high-temperature Si sublimation [1]), which guarantees cleaner and more uniform edges. At low magnetic fields, the MR curve shows evidence for weak localization due to intervalley scattering from the sharp edges. With increasing magnetic field, quantum transport described by boundary scattering in the quasi-ballistic regime can be observed [2]. The scattering mechanism of self-organized ribbons is totally different from that of the etched one due to the edge effects.

References
[1] T. Ohta et al., Phys. Rev. B 81, 121411(R) (2010)
[2] T. J. Thornton et al., Phys. Rev. Lett. 63, 2128 (1989)