Transfer-Free, Large-Scale Growth of High-Quality Graphene on Insulating Substrate by Physical Contact of Copper Foil.

High-quality, large-area, single-layer graphene was directly grown on top of a quartz substrate by a low-pressure chemical vapor deposition (CVD) process using Cu vapor as a catalyst. In this process, continuous generation and supply of highly concentrated Cu vapor is the key to the growth of large-scale, high-quality graphene. It was achieved by direct physical contact, or "touch-down," of a Cu foil with an underlying sacrificial SiO2 /Si substrate, and the target quartz substrate was placed on top of the Cu foil, eventually having a quartz/Cu/SiO2 /Si sandwich structure. To establish the reaction mechanism, a test growth was performed without the quartz substrate, which revealed that Cu is diffused through the SiO2 layer of the sacrificial SiO2 /Si substrate to form liquid-phase Cu-Si alloy that emits massive Cu vapor. This Cu vapor catalyzes thermal decomposition of supplied CH4 gas.