Browsing by Author "Iacopi, F"

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    Epitaxial graphene growth on cubic silicon carbide on silicon with high temperature neutron reflectometry: an operando study
    (Royal Society of Chemistry, 2024-01-19) Pradeepkumar, A; Cortie, DL; Smyth, E; Le Brun, AP; Iacopi, F
    The growth of graphene on silicon carbide on silicon offers a very attractive route towards novel wafer-scale photonic and electronic devices that are easy to fabricate and can be integrated in silicon manufacturing. Using a Ni/Cu catalyst for the epitaxial growth of graphene has been successful in the mitigation of the very defective nature of the underlying silicon carbide on silicon, leading to a consistent graphene coverage over large scales. A more detailed understanding of this growth mechanism is warranted in order to further optimise the catalyst composition, preferably via the use of operando characterization measurements. Here, we report in situ neutron reflectometry measurements of (Ni, Cu)/SiC films on silicon wafers, annealed from room temperature to 1100 °C, which initiates graphene formation at the buried (Ni, Cu)/SiC interface. Detailed modelling of the high temperature neutron reflectometry and corresponding scattering length density profiles yield insights into the distinct physical mechanisms within the different temperature regimes. The initially smooth solid metallic layers undergo intermixing and roughening transitions at relatively low temperatures below 500 °C, and then metal silicides begin to form above 600 °C from interfacial reactions with the SiC, releasing atomic carbon. At the highest temperature range of 600–1100 °C, the low neutron scattering length density at high temperature is consistent with a silicon-rich, liquid surface phase corresponding to molten nickel silicides and copper. This liquid catalyst layer promotes the liquid-phase epitaxial growth of a graphene layer by precipitating the excess carbon available at the SiC/metal interface. © The Authors - Open Access CC BY-NC
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    A high temperature operando study of epitaxial graphene growth on cubic silicon carbide using neutron reflectometry
    (Taylor & Francis, 2024-05-30) Pradeepkumar, A; Cortie, DL; Smyth, E; Le Brun, AP; Iacopi, F
    The synthesis of epitaxial graphene (EG) on cubic silicon carbide on silicon substrates holds vast promise for scalable graphene-based electronics and photonics applications integrated with silicon technology. The 3C-SiC/silicon platform is particularly challenging due, among other factors, to the highly defective nature of the 3C-SiC [Citation1]. We have pioneered the use of a Ni/Cu catalyst to obtain a continuous coverage of graphene despite the defective cubic silicon carbide surface template, inferring that this considerable improvement was also to the liquid-phase epitaxial growth condition at 1100°C [Citation2]. A detailed understanding of the graphene growth mechanism through operando analysis is critical in order to optimize further the Ni/Cu catalyst composition and further refine the graphene synthesis process. © 2024Informa UK Limited
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    Quasi free-standing graphene growth on FIB-Patterned 3C-SiC nanostructures
    (Australian Institute of Physics, 2018-01-30) Amjadipour, M; Tadich, A; MacLeod, J; Lipton-Duffin, J; Iacopi, F; Motta, N
    There is a growing body of literature that recognizes the potential of graphene for use in electronics. However, graphene’s lack of bandgap challenges its remarkable range of applications. Theoretical work suggests that a bandgap might be opened in graphene through quantum confinement, for example in graphene nanoribbons. Thermal decomposition of SiC has proven to be an excellent method to grow transfer-free wafer-scale graphene. Growing graphene on SiC thin films on Si is a cheaper alternative to the growth on bulk SiC. In this research we attempt to manipulate the SiC substrate dimension to grow graphene over nanostructures and use hydrogen intercalation to produce quasi free-standing graphene. SiC mesas have been fabricated by patterning SiC/Si substrates using Focused Ion Beam (FIB) milling. Hydrogen intercalation procedure has been employed at 600 °C to fabricate free-standing graphene on the structures. Synchrotron radiation near-edge X-ray absorption fine structure (NEXAFS) with core-level photoelectron spectroscopy (PES), scanning tunnelling microscopy (STM), scanning electron microscopy (SEM), and Raman spectroscopy were used to investigate the process. Our result indicates the possibility of growing free-standing epitaxy graphene over SiC nanostructures. However, more research is needed to better understand the impact of patterning procedure on the graphene growth and decrease the damage caused by milling process.