Effect of a Balanced Concentration of Hydrogen on Graphene CVD Growth

Abstract

The extraordinary properties of graphene make it one of the most interesting materials for future applications. Chemical vapor deposition (CVD) is the synthetic method that permits obtaining large areas of monolayer graphene. To achieve this, it is important to find the appropriate conditions for each experimental system. In our CVD reactor working at low pressure, important factors appear to be the pretreatment of the copper substrate, considering both its cleaning and its annealing before the growing process. The carbon precursor/hydrogen flow ratio and its modification during the growth are significant in order to obtain large area graphene crystals with few defects. In this work, we have focused on the study of the methane and the hydrogen flows to control the production of single layer graphene (SLG) and its growth time. In particular, we observe that hydrogen concentration increases during a usual growing process (keeping stable the methane/hydrogen flow ratio) resulting in etched domains. In order to balance this increase, a modification of the hydrogen flow results in the growth of smooth hexagonal SLG domains. This is a result of the etching effect that hydrogen performs on the growing graphene. It is essential, therefore, to study the moderated presence of hydrogen.

Annealing effect on UV-illuminated recovery in gas response of graphene-based NO2 sensors

“…The graphene surface coverage and the graphene domain size were also evaluated in the same way. 51 Based on the above results of Raman spectrum, Hall measurement and surface roughness by AFM, the PMMA could be almost removed at an RTA temperature of 300 C. The RTA temperature at 400 C could form amorphous carbon on the graphene surface leading to a high surface roughness.…”

Impact of the in situ rise in hydrogen partial pressure on graphene shape evolution during CVD growth of graphene

“…Indications of the local increase of H 2 with growth time have been also observed in a recent paper. 22 In our experiment, the excess H 2 enhances graphene etching from the edges: because of the functional groups and dangling bonds, the chemical reactivity of graphene edge carbon atoms is higher than the perfectly bonded carbon atoms in the basal plane. 23 …”

Recent Developments in Graphene and Graphene Oxide: Properties, Synthesis, and Modifications: A Review

“…The conditions employed in the process vary with different carbon source gases including methane, [104] methane-hydrogen, [105] methane-hydrogen-argon. [106,107] Exposure of a transition metal substrate to a hydrocarbon gas under high temperature leads to graphene nucleation and growth. In the first CVD report in 2009 from Massachusetts Institute of Technology, [108] attempts to synthesize an ultrathin graphene film with 1 to˜10 layers used a nickel film at 900-1000°C, with hydrocarbon flow at high dilution.…”