Mechanism of Thin Layers Graphite Formation by 13C Implantation and Annealing

Abstract

Abstract:The mechanism of thin layers graphite (TLG) synthesis on a polycrystalline nickel film deposited on SiO 2 (300 nm thick)/Si(100) has been investigated by 13 C implantation of four equivalent graphene monolayers and annealing at moderate temperatures (450-600 °C). During this process, the implanted 13 C segregates to the surface. NuclearReaction Analyses (NRA) are used for the first time in the topic of graphene synthesis to separate the isotopes and to determine the 12 C and 13 C concentrations at each step. Indeed, a significant part of carbon in the TLG also comes from residual 12 C carbon absorbed into the metallic matrix. Raman spectroscopy and imaging are used to determine the main location of each carbon isotope in the TLG. The Raman mappings especially emphasize the role of 12 C previously present at the surface that first diffuses along grain boundaries. They play the role of nucleation precursors. Around them the implanted 13 C or a mixture of bulk 12 C-13 C aggregate and further precipitate into graphene-like fragments. Graphenization is effective at around 600 °C. These results point out the importance of controlling carbon incorporation, as well as the importance of preparing a uniform nickel surface, in order to avoid heterogeneous nucleation.

Graphene Thin Layers Formation on Monocrystalline Ni(111)/MgO(111) by Carbon Implantation and Annealing

“…Different steps of the experiment have been already reported elsewhere [22] [23] and the overall pathway is summarized in Figure 1, including Ni film preparation (top), carbon implantation and thermal annealing (bottom). Finally the carbon has been etched by Reactive Ion Etching and the metallic film is dissolved into a 2 M FeCl 3 ethanol solution, according to a process described in the literature [12], so that these substrates can be reused.…”

“…It can be seen that 12 C is incorporated into the film both during the nickel deposition (black curve of the 12 C(d, p 0 ) 13 C inset) as well as during the implantation itself (red curve of the 12 C(d, p 0 ) 13 C inset). This has been already shown with polycrystalline nickel films evaporated on SiO 2 /Si [23]. The raw signals must be corrected by the NRA cross-sections which are 25.9 mb/sr [32] and 2.36 mb/sr [33] for 12 C(d, p) 13 C and 13 C(d, p) 14 C reactions, respectively.…”

“…Dark fragments corresponding to TLG with sizes ≤ 2 µm 2 are located mainly around grain boundaries and are not very well-defined. On both samples TLG fragments are mainly relied to the presence of grain boundaries and other point defects, as for polycrystalline Ni films [23]. Preferential nucleation occurs due to preferential carbon diffusion along these grain boundaries or defects.…”

“…Previous works [23] have shown that many carbon impurities are incorporated into the Ni films during the Ni growth as well as during the carbon implantation process, leading to an excess of carbon. To disentangle between the true carbon coming from the implantation process and the pollution carbon incorporated at any step of the process, we have used the 13 C isotope, which is only 1.07% of natural carbon.…”

“…The carbon implantation process to form graphene film has been soon described in the literature, but using polycrystalline Ni films [16]- [23]. Then high-quality graphene or TLG are obtained but with variable thickness and weak size domains.…”