Browsing by Author "Dhaouadi E."

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    Erratum: Computer-aided design of graphene and 2D materials synthesis via magnetic inductive heating of 11 transition metals (J. Phys. D: Appl. Phys. (2021) 55 (105302) DOI: 10.1088/1361-6463/ac357d)
    (2022-04-14) Dhaouadi E.; Hinkov I.; Pashova K.; Challab N.; Roussigné Y.; Abderrabba M.; Farhat S.
    There was a typo during the production of our paper. The alpha factor has been omitted from equation (3). The equation should appear as follows: ρ = ρ0 (1 + αT).
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    Graphene synthesis by electromagnetic induction heating of oxygen-rich copper foils
    (2023-02-01) Dhaouadi E.; Alimi W.; Konstantakopoulou M.; Hinkov I.; Abderrabba M.; Farhat S.
    We report in this article an optimized synthesis of high-quality monolayer graphene by chemical vapor deposition (CVD) using methane as carbon source. The synthesis occurs on a centimeter-sized copper substrate previously oxidized in air at 180 °C then heated by electromagnetic induction in a controlled atmosphere of argon and hydrogen in which the steady-state temperature of ∼1050 °C is reached after only ∼2 min heating from room temperature. The rapidity of the heating and cooling process highlights the advantage of using the electromagnetic induction heating method in order to achieve the synthesis of graphene. When applied to CVD, electromagnetic inductive heating only heats the metallic substrate avoiding energy losses in the reaction medium. Therefore, inductive heating has great potential for large-scale and rapid manufacturing of graphene and 2D materials. This work includes an experimental study that consists in comparing the quality of the synthesized graphene over different substrates ranging from oxygen-free copper foil to oxidized copper with the aim to reduce the defects in the graphene and also to increase the domain size. We find that copper with an oxidized surface can drastically reduce graphene nucleation density thereby increasing the graphene domain sizes. In addition, we demonstrated experimentally and by numerical simulations that the presence of a thin layer of copper oxide does not disturb the mechanism of induction heating allowing the growth of high-quality graphene films by inductive heating of copper oxides. Graphene quality was studied by Raman spectroscopy, and scanning electron microscopy (SEM) which respectively showed very little defective monolayer graphene (ID / IG < 0.2) and non-defective graphene subdomains of average size ranging from ∼5 μm to∼10 μm which is comparable, if not better, to traditional thermal CVD method. These results provide directions for effective control of the defects and layers of graphene.
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    Graphene synthesis by electromagnetic induction heating: Domain size and morphology control
    (2024-04-01) Dhaouadi E.; Alimi W.; Hinkov I.; Abderrabba M.; Farhat S.
    In this paper we discuss the effect of hydrogen and methane content during low-pressure chemical vapor deposition (LPCVD) of graphene on inductively heated copper foils. By increasing the H2/CH4 ratio by a factor of 5 from 25 to 125, different graphene morphologies ranging from dendritic fractals to compact hexagonal islands are obtained. In addition, increasing the hydrogen concentration allows the nucleation rate to be slowed down by a factor of ∼10 thereby high-quality regular hexagonal graphene single crystals of significant size of 0.1 mm are found. From these measurements, we estimate the activation energy for graphene nucleation in low-pressure CVD (2 eV) and propose a phenomenological law for graphene nucleation. As compared to conventional CVD methods, considerable advantages of inductive heating are outlined, and some fundamental aspects of this approach are discussed.
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    Graphene synthesis by inductively heated copper foils: Reactor design and operation
    (2020-04-01) Pashova K.; Dhaouadi E.; Hinkov I.; Brinza O.; Roussigné Y.; Abderrabba M.; Farhat S.
    We report on the design of a reactor to grow graphene via inductively heating of copper foils by radio frequency (RF) magnetic fields. A nearly uniform magnetic field induced by Helmholtz-like coils penetrates the copper foil generating eddy currents. While the frequency of the current is being rapidly varied, the substrate temperature increases from room temperature to ~1050 °C in 60 s. This temperature is maintained under Ar/H2 flow to reduce the copper, and under Ar/H2/CH4 to nucleate and grow the graphene over the entire copper foil. After the power cut-off, the temperature decreases rapidly to room temperature, stopping graphene secondary nucleation. Good quality graphene was obtained and transferred onto silicon, and coated with a 300 nm layer of SiO2 by chemical etching of the copper foil. After synthesis, samples were characterized by Raman spectroscopy. The design of the coils and the total power requirements for the graphene induction heating system were first estimated. Then, the effect of the process parameters on the temperature distribution in the copper foil was performed by solving the transient and steady-state coupled electromagnetic and thermal problem in the 2D domain. The quantitative effects of these process parameters were investigated, and the optimization analysis results are reported providing a root toward a scalable process for large-sized graphene.