Ethanol-CVD Growth of Sub-mm Single-Crystal Graphene on Flat Cu Surfaces

High-quality graphene can be produced in 10 large scale by chemical vapor deposition (CVD). Ethanol is 11 emerging as a versatile carbon source alternative to methane 12 for the growth of graphene on a copper (Cu) foil catalyst. To 13 date, rigorous studies of the ethanol-based process still lack, 14 especially concerning the first stages of the growth, which 15 ultimately determines graphene’s properties, such as defect 16 density and crystal size, and performance, such as electrical 17 conductance and mechanical strength. In particular, so far the 18 growth of isolated graphene grains by ethanol-CVD has been 19 achieved only on preoxidized Cu foils folded in enclosures, in an attempt to limit the partial pressure of the precursor, and thus 20 the nucleation rate. We herein systematically explored the process parameters of ethanol-CVD to obtain full control over the 21 nucleation rate, grain size, and crystallinity of graphene on flat Cu foils, which are of interest for any realistic production in large 22 scale. To limit the nucleation density and increase the grain size, preoxidized Cu foils (250 °C in air) were used as substrates, 23 and the process parameters were thoroughly investigated and tuned. Ultimately, at an ethanol vapor flow of 1.5 × 10−3 sccm, the 24 nucleation density was reduced to less than 3 nuclei/mm2 and isolated single-crystal grains were grown with a lateral size above 25 350 μm. When transferred onto Si/SiO2 substrates, the grains showed field-effect mobility beyond 1300 cm2/(V s). Our results 26 provide a step closer towards an affordable commercialization of electronic-grade, large-area graphene.