Direct formation of graphene on dielectric substrate: Controlling the location of graphene formation adopting carbon diffusion barrier

Abstract

The authors report a method to form multilayered graphene directly on top of a dielectric SiO2/Si substrate by the solid-phase crystallization of amorphous carbon (a-C) using Ni as a catalyst and Ti as a carbon diffusion barrier layer; the layer sequence is Ti/Ni/a-C/SiO2/Si. During annealing, carbon diffuses through Ni and forms TiC at the Ti/Ni interface, blocking further carbon diffusion to the Ti layer. During cooling, the remnant carbon in the Ni layer precipitates out at the Ni/SiO2 interface, forming multilayers of graphene. Then, both Ti and Ni are etched away using Radio Corporation of America standard cleaning (SC-I) and FeCl3-based wet etching. The graphene layers formed on top of the dielectric substrate can be utilized without further transfer methods. The best-quality of graphene is formed at 600 °C with the Raman signal D- to G-peak intensity ratio of 0.29. Auger electron spectroscopy depth profiles and sequential etching tests with SC-I and FeCl3-based etchant confirms that the Ti layer is transformed to TiOxCy or TiC layer, which may reduce the carbon diffusion flux through this layer, as expected.