High-Temperature Growth of Graphene Films on Copper Foils by Ethanol Chemical Vapor Deposition

Abstract

Chemical vapor deposition (CVD) is widely utilized to synthesize graphene with controlled properties for many applications, especially when continuous films over large areas are required. Although hydrocarbons such as methane are quite efficient precursors for CVD at high temperature (∼1000 °C), finding less explosive and safer carbon sources is considered beneficial for the transition to large-scale production. In this work, we investigated the CVD growth of graphene using ethanol, which is a harmless and readily processable carbon feedstock that is expected to provide favorable kinetics. We tested a wide range of synthesis conditions (i.e., temperature, time, gas ratios), and on the basis of systematic analysis by Raman spectroscopy, we identified the optimal parameters for producing highly crystalline graphene with different numbers of layers. Our results demonstrate the importance of high temperature (1070 °C) for ethanol CVD and emphasize the significant effects that hydrogen and water vapor, coming from the thermal decomposition of ethanol, have on the crystal quality of the synthesized graphene.

In situ control of dewetting of Cu thin films in graphene chemical vapor deposition

“…In other words, graphene is grown during a prolonged dewetting incubation time. Differently from foils, in which the graphene quality is highly dependent on the temperature (around 1000 °C), no matter if in the pre-deposition [26] or deposition [19] step, our results demonstrate that Cu films can be efficiently activated at lower T values and the process can be fully controlled by adjusting several parameters (besides the film thickness and T) like the pressure in chamber, the gas composition, and the pre-deposition duration. and foil (with hard recipe in this case, but results do not depend on the pre-treatment).…”

“…Such high T values seem necessary, even in cases where C precursors catalysing at lower T are employed [19]. At such T values, moreover, consistent Cu sublimation occurs, the Cu vapour pressure reaching 10 -2 Pa [1].…”

“…To achieve optimal results, several parameters have to be finely adjusted, namely, film thickness, temperature, pressure chamber, and gas composition and fluxes in both pre-deposition and deposition steps. As an example, no H2 is added to carbon source during deposition, as it has been proved that small amounts of H2 can be beneficial to the graphene's quality [19]. In both the recipes, a Cu foil has been added in the deposition chamber as a control, to evidence the different surface behaviour of the two systems.…”

Rapid and highly efficient growth of graphene on copper by chemical vapor deposition of ethanol

“…In particular, the 650-850°C and 900°C ranges were investigated (respectively, for 5 and 30 min growth time) [8,9]. Recently, our group reported the growth of highly-crystalline, few-layer graphene by CVD of ethanol at high temperatures (1000-1070°C), using growth times typical of CH 4 -assisted growth (10-30 min) [14]. Another recent paper reported a self-limiting growth of graphene from ethanol occurring after 5 min at 1000°C; however, this was achieved in copper foil enclosures (different from plain copper surfaces), specifically designed to reduce the gas partial pressure at the catalyst surface [15].…”

Growth Conditions of Graphene Grown in Chemical Vapour Deposition (CVD)

“…Therefore, mass production of high quality graphene is a must. In recent years, CVD have shown the capability to produce graphene in large scale with promising quality by using Cu as the catalyst or substrate to decompose hydrocarbon gas such as methane, CH 4 (Chan et al 2013;Faggio et al 2013;Li et al 2009)graphene is limited to small sizes because it is produced mostly by exfoliating graphite. We grew large-area graphene films of the order of centimeters on copper substrates by chemical vapour deposition using methane.…”