Gas-phase dynamics in graphene growth by chemical vapour deposition

Abstract

Chemical vapour deposition on a Cu substrate is becoming a very important approach to obtain high quality graphene samples. Previous studies of graphene growth on Cu mainly focus on surface processes. However, recent experiments suggest that gas-phase dynamics also plays an important role in graphene growth. In this article, gas-phase processes are systematically studied using computational fluid dynamics. Our simulations clearly show that graphene growth is limited by mass transport under ambient pressures while it is limited by surface reactions under low pressures. The carbon deposition rate at different positions in the tube furnace and the concentration of different gas phase species are calculated. Our results confirm that the previously realized graphene thickness control by changing the position of the Cu foil is a result of gas-phase methane decomposition reactions.

Fast Growth and Broad Applications of 25‐Inch Uniform Graphene Glass

“…This renders our process 5–23 times faster than the traditional APCVD method employing methane as the precursor. Further, great improvement of the surface‐deposition rate can be achieved by the LPCVD route as compared to the APCVD route when the growth temperature increases (Section S1, Supporting Information) . Consequently, our proposed route has a clear advantage over the APCVD route for synthesis at elevated temperature.…”

“…In this study, we developed an ethanol‐precursor‐based low‐pressure CVD (LPCVD) route for the fast and economical synthesis of highly uniform, large‐area, and thickness‐controllable graphene glass. The uniqueness of this route lies in the fact that: i) the LPCVD system allows for improvements in the mass‐transport rate and concentration uniformity of the active carbon species in the growth zone in contrast to the case for the APCVD route, which results in graphene films with significantly enhanced growth efficiency and thickness uniformity across large areas, and ii) the thermal decomposition rate of ethanol is rather high at temperature greater than 800 °C, which ensures the presence of the active carbon species in a sufficient amount for the nucleation and growth of graphene under the low‐pressure conditions. As a result, a 25‐inch uniform graphene‐glass sample was produced within 4 min, the production efficiency of which was ≈20 times faster than that from the methane‐precursor‐based APCVD method.…”

“…It is known that, under low‐pressure conditions, the rate determining step for the CVD growth of graphene is the surface reactions, given the rather high mass‐transport rate . This is actually attributed to the high diffusivity of the active carbon species in the low‐density environment . In contrast, under atmospheric‐pressure conditions, the mass‐transport rate is limited, since the transport coefficient is several orders of magnitude smaller than that under low‐pressure conditions .…”

“…This is actually attributed to the high diffusivity of the active carbon species in the low‐density environment . In contrast, under atmospheric‐pressure conditions, the mass‐transport rate is limited, since the transport coefficient is several orders of magnitude smaller than that under low‐pressure conditions . Hence, the LPCVD route is, in general, more suitable for the fast deposition of graphene.…”

“…In contrast, the growth efficiency is much lower when methane is used as the precursor: at the nucleation stage, nuclei are not observed until a synthesis time of 30 min; furthermore, it is difficult to obtain full‐coverage graphene films on glass even after 80 min. In this regard, it is worth noting that the growth efficiency corresponding to the ethanol‐precursor‐based LPCVD route is ≈20 times higher than that for the methane‐precursor‐based APCVD route …”