Suppression of Nucleation Density in Twisted Graphene Domains Grown on Graphene/SiC Template by Sequential Thermal Process

We investigated the growth of twisted graphene on graphene/silicon carbide (SiC-G) templates by metal-free chemical vapor deposition (CVD) through a sequential thermal (ST) process, which exploits the ultraclean surface of SiC-G without exposing the surface to air before CVD. By conducting control experiments with SiC-G templates exposed to air (AirE process), structural analysis by atomic force microscopy revealed that the nucleation density of CVD-grown graphene (CVD-G) was significantly suppressed in the ST process under the same growth conditions. The nucleation behavior on SiC-G surfaces was observed to be very sensitive to the carbon source concentration and process temperature. Nucleation on the ultraclean surface of SiC-G prepared by the ST process requires a higher partial pressure of the carbon source compared to that on the surface of SiC-G prepared by the AirE process. Moreover, an analysis of CVD-G growth over a wide temperature range indicated that the nucleation phenomena change dramatically with a threshold temperature of 1300 °C, possibly due to arising etching effects. The successful synthesis of twisted few-layer graphene (tFLG) was affirmed by Raman spectroscopy, in which an analysis of the G′-band proved thre was a high ratio of twisted structure in CVD-G. These results demonstrate that metal-free CVD utilizing ultraclean templates is an effective approach for the scalable production of large-domain tFLG, which is valuable for electronic applications.