Growth Phase Diagram of Graphene Grown Through Chemical Vapor Deposition on Copper.

The phase diagram for graphene growth was obtained to understand the physics of the growth mechanism and control the layer number or coverage of graphene deposited on copper via low-pressure chemical vapor deposition (LPCVD). Management of the number of graphene layers and vacancies is essential for producing defect-free monolayer graphene and engineering multilayered functionalized graphene. In this work, the effects of the CH4 and H2 flow rates were investigated to establish the phase diagram for graphene growth. Using this phase diagram, we selectively obtained fully covered and partially grown monolayer graphene, graphene islands through Volmer–Weber growth, and multilayer graphene through Stranski–Krastanov-like growth. The layer numbers and coverage were determined using optical microscopy, scanning electron microscopy, transmission electron microscopy, atomic force microscopy and Raman spectroscopy. The growth modes were determined by the competition between catalytic growth with CH4 and catalytic etching with H2 on the copper surface during CVD growth. Intriguingly, this phase diagram showed that multilayer graphene flakes can be grown via LPCVD even with low CH4 and H2 flows. The role of CH4 and H2 gas flow rates on the graphene growth via CVD on copper was studied. The various growth phases with different CH4 and H2 gas flow rates are marked on the growth phase diagram. The graphene growth on copper is dominated by the island growth mode for low H2 gas flow rates. The quality and the number of graphene layers can be controlled by the gas flow rates of CH4 and H2. [ABSTRACT FROM AUTHOR]