Chemical Vapour Deposition Growth of Graphene and Hexagonal Boron Nitride, and a Study of the Electronic and Corrosion Inhibiting Properties of Hexagonal Boron Nitride

Download or read book Chemical Vapour Deposition Growth of Graphene and Hexagonal Boron Nitride, and a Study of the Electronic and Corrosion Inhibiting Properties of Hexagonal Boron Nitride written by Farzaneh Mahvash Mohammadi and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "Graphene is an allotrope of carbon in the form of a two-dimensional (2D) material with zero bandgap. Hexagonal boron nitride (hBN), also known as white graphite, is a wide bandgap 2D material that has found use as an insulating dielectric layer in ultra-high mobility graphene devices, 2D heterostructures and tunneling devices. In this thesis, we report the chemical vapor deposition (CVD) growth and characterization of graphene and monolayer hBN. The growth of graphene and hBN was performed separately in a tube furnace on Cu foils using methane (CH4) and an ammonia borane (NH3-BH3) precursor, respectively. Raman spectroscopy confirmed that the CVD grown graphene is a monolayer of high quality. We have fabricated graphene field effect transistors and characterized their electrical properties to demonstrate material quality. Additionally, the CVD grown graphene was incorporated in a diverse range of applications, including large area graphene ion sensitive field effect transistors, suspended graphene varactors and an investigation of the role of hydrogenation on the electronic and thermal properties of graphene. We employed a variety of techniques to characterize CVD grown hBN. The morphology of the as-grown film along with the optimization of growth conditions to yield high coverage of monolayer hBN was studied by scanning electron microscopy. X-ray photoelectron spectroscopy confirmed the presence of boron and nitrogen in the CVD grown film as well as the expected stoichiometry. The electron diffraction pattern of suspended hBN films displayed a hexagonal crystal structure. A prominent Stokes Raman shift at 1369 cm-1 was observed in hBN transferred to Si/SiO2 substrates, revealing that our CVD grown hBN is of monolayer form. The optical properties of our hBN layers were probed by cathodoluminescence and UV-visible absorption spectroscopy. We report the first observation of in-plane charge transport in large area CVD grown monolayer hBN using a variety of electrode geometries. Ni electrodes were used to provide electrical contacts. We have observed a quadratic scaling of current with voltage at high bias corresponding to a space charge limited conduction mechanism, with a room temperature mobility reaching up to 0.01 cm2/Vs at electric fields up to 100 kV/cm in the absence of dielectric breakdown. The observation of in-plane charge transport highlights the semiconducting nature of monolayer hBN, and identifies hBN as a wide-gap 2D crystal capable of supporting charge transport at high field. Furthermore, we have examined the suitability of CVD grown monolayer hBN for inhibiting corrosion. Quantitative measurements of monolayer hBN as a Cu corrosion inhibitor were studied by use of cyclic voltammetry, Tafel analysis and electrochemical impedance spectroscopy. We have found that CVD grown monolayer hBN reduces the Cu corrosion rate by one order of magnitude compared to bare Cu, suggesting that this ultrathin layer can be employed as an atomically thin corrosion-inhibition coating.The final contribution of this thesis is the growth of hBN directly on Si/SiO2 substrate via CVD. The main focus of this work is to produce metal-free, large-area, continuous and uniform hBN dielectric films on Si-based substrates ready to incorporate into devices without any transfer processing. We have also examined the effect of carrier gas flow rate on the thickness and roughness of the grown film in atmospheric pressure CVD. We have succeeded to grow large area hBN films with the thickness of ~ 2 nm and rms roughness of 0.6 nm (over 1 μm2) directly on Si/SiO2 substrates via atmospheric pressure CVD." --