Characterization of graphene grown on copper foil by chemical vapor deposition (CVD) at ambient pressure conditions

Abstract

In the aim to get high quality graphene films, with large domains and free from impurities, minimizing also the manufacturing costs, we investigate the graphene grown on copper (Cu) foil by chemical vapor deposition at ambient pressure conditions, by using methane (CH4) as carbon source, diluted in a suitable mixture of argon (Ar) and hydrogen (H2). Several graphene samples were synthesized, for variable exposure times to hydrocarbon precursor, in the range from 1 min to 1 hr. The quality of the graphene films and their structural, morphological, and electronic properties were evaluated by micro‐Raman spectroscopy and other techniques, including, scanning tunneling microscopy, atomic force microscopy, and scanning electronic microscopy. In particular, samples obtained with shorter growth time (less than 10 min) exhibit a non‐uniform coverage of the Cu surface, whereas those synthesized with exposure time between 10 and 30 min show a prevalence of well‐ordered monolayer graphene domains. For longer deposition, the amount of disordered domains increases, as revealed by Raman analysis, and the resulting film shows a nonself‐limiting growth behavior for chemical vapor deposition at atmospheric conditions. In addition, we observed 2 kinds of monolayer graphene, in terms of coupling with the Cu surface, for the samples synthesized between 10 and 30 min. To the best of our knowledge, “coupled” and “decoupled” graphene regions have never been reported at the same time on Cu surface. Furthermore, a Raman statistical analysis has been performed on the G and 2D bands measured in both the kinds of regions, gaining evidence of a bimodal behavior for the graphene spots, corresponding to “coupled” and “decoupled” configurations. This difference, which is appreciable also by the optical microscopy inspection, could be related to the local Cu oxidation and to oxygen intercalation after graphene growth.

Different spectroscopic behavior of coupled and freestanding monolayer graphene deposited by CVD on Cu foil

“…Color differences appear also to the optical microscope (see Fig. 1(b)), in similar way to previous observations made for ambient pressure CVD graphene on copper [35]. In the present case, comparable size of the "dark" and "bright" areas (10 3 -10 4 μm 2 ) are observed.…”

Raman study of the substrate influence on graphene synthesis using a solid carbon source via rapid thermal annealing

“…In this way, the specific effect of the substrate on graphene‐based films nanoarchitecture can be assessed, because identical deposition and heating processes are used for both substrates. The films are usually characterized by Raman microspectroscopy, a recognized technique for investigating the nanostructure, crystallite size, defects, and number of layers in graphene materials . Specifically, surface mapping of the Raman signal is performed to accurately assess the homogeneity of the samples at the micrometric scale.…”

The synthesis of graphene coated copper from PMMA and the anticorrosion performance of copper substrate

“…The broad XPS spectrum clearly shows a C1s peak at about 284.5 eV, an O1s peak at about 531 eV, a Cu LMM peak at about 570 eV, a Cu 2p 3/2 peak near 932 eV, and a Cu 2p 1/2 peak at about 951.2 eV. The presence of oxygen is caused by the migration of oxygen dissolved in the interior of the copper foil to the surface during growth, and the results of the graphene films prepared under different conditions are almost the same [36]. Figures 4(b)-(d) show the XPS spectra of the photoelectron-emitting graphene film of the C1S nuclear level peak under different growth conditions (800°C, 700°C, 600°C), the peak consisting of two components, The carbon bond group is hybridized by SP 3 at a binding energy of 284.5 eV, C=C SP 2 bond in the graphite network, and another at 285.6 eV.…”