Surface Termination and Graphitisation of Nanodiamonds

Abstract

This thesis describes the graphitisation and further modification of diamond and nanodiamond surfaces that have been investigated in-situ using multiple photoelectron spectroscopy techniques, including real-time and near-ambient pressure X-ray photoelectron spectroscopy. The low-temperature graphitisation of boron-doped polycrystalline diamond to produce multilayer graphene was demonstrated using real-time photoelectron spectroscopy by annealing the sample in-situ, in an ultra-high vacuum. A thin overlayer of iron of approximately 10 nm was deposited to catalytically lower the conversion temperature of sp3 to sp2 carbon. The iron overlayer interacted with nickel present on the surface of the polycrystalline diamond to further reduce the onset graphitisation temperature to lower than had been previously demonstrated for single-crystal substrates. X-ray photoelectron spectroscopy and Raman spectroscopy was used to characterise the graphene. Both the non-catalytic and catalytic graphitisation of hydrogen-terminated nanodiamonds were investigated by annealing the nanodiamond samples in an ultra-high vacuum and monitored in real-time. When a thin iron overlayer was deposited onto the nanodiamond film, multi-layer graphene/HOPG was produced demonstrating that the process of producing graphene on singlecrystal and polycrystalline diamond samples can be extended to nanodiamonds. Amine-terminated nanodiamonds were annealed in pure hydrogen gas and measured using nearambient pressure X-ray photoelectron spectroscopy and near-edge X-ray absorption fine structure spectroscopy. During the anneal to 500 oC, the surface of the nanodiamonds were further modified where the potential encapsulation of nitrogen from the amine groups to between the sub-surface and surface layers of nanodiamond was observed in XPS.

Date of Award	2021
Original language	English
Awarding Institution	Aberystwyth University
Sponsors	Engineering and Physical Sciences Research Council
Supervisor	Andrew Evans (Supervisor) & Rachel Cross (Supervisor)