Hunt, MichaelAlsulami, Taghreed Sulaiman2023-11-142023-11-142023-10-12https://hdl.handle.net/20.500.14154/69686The growth of two-dimensional materials by low-cost atmospheric pressure chemical vapour deposition (AP-CVD) is explored in this thesis, with an emphasis on understanding key features of the growth process. In particular, the growth of graphene on copper foils using a methane precursor, MoS2 on natively oxidised silicon and MoS2 on graphene, graphite and graphene ‘paper’ were studied. The resulting few-layer, monolayer and sub-monolayer films were characterised by a combination of Raman spectroscopy (RS), Scanning Electron Microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Through varying the methane flow rate it was found that there is no self-limitation to graphene growth at high methane concentrations, resulting in graphene multilayers that can delaminate from the copper substrate. The effect of a number of surface pre-treatments on graphene growth is also presented. Nitric acid etching of copper foil was found to produce a superior growth surface in comparison with those prepared with acetic acid or electropolishing, evidenced by a reduction in nucleation density and increased island size. Raman spectra showed a remarkable correlation with these observations, indicating increased hole doping with improved sample treatment. Therefore, Raman spectroscopy may be used as a probe for the effectiveness of surface preparation. Several different approaches to the growth of MoS2 on natively oxidised silicon by AP-CVD using S and MoO3 precursors are presented. It was found that the growth of MoS2 was strongly dependent on the timing with which a sufficient sulphur flux is introduced into the growth region. These results led to an investigation into the influence of sulphur partial vapour pressure on MoS2 growth. It was found that MoS2 coverage decreased with increasing sulphur vapour pressure. These results could be successfully rationalised by the Langmuir-Hinshelwood model of growth kinetics, which is usually applied to reactions on well-defined crystalline surfaces and had not previously been considered for MoS2 growth. XPS was used to study the composition of AP-CVD grown MoS2 as a function of sulphur evaporation temperature and provided clear evidence that lower sulphur vapour pressure leads to an increased concentration of sulphur vacancy defects. Attempts were made to grow MoS2 directly on highly oriented pyrolytic graphite as a model substrate. MoS2 was found to grow on graphite under similar conditions to those for natively oxidised silicon, but nucleation was observed to occur primarily at defect (step) sites. Attempts to grow MoS2 directly on graphene CVD grown on copper, commercially sourced graphene powder, and graphene paper are also reported.159engrowth of two-dimensional materialsChemical Vapour Deposition (CVD)GrapheneMoS2Thesis