AbstractThis thesis ‘’Heterostructures from Chemical Vapour Deposition. The Synthesis and Characterisation of Tungsten and Tin Chalcogenides on Graphene Substrates.’’ encompasses a range of research areas, all under the umbrella of chemical vapour deposition (CVD). Within this report, two types of deposition techniques are compared, high temperature CVD and aerosol assisted CVD (AA-CVD). Chapter 1 presents an up-to-date review of the literature landscape pertaining to graphene and graphene-like materials, including their history, synthesis and properties. Additionally, the various CVD techniques and growth mechanisms are presented.In Chapter 2 we describe the design and use of a CVD reactor to produce graphene. It was found through optimisation of reaction conditions, graphene could be grown on cm length scales on copper foil. Graphene samples were then successfully transferred onto SiO2 substrates, onto which tin sulphides and tungsten disulphide could be grown. An atomic layer deposition (ALD) technique was also used to deposit graphitic carbon films onto copper foil at temperatures as low as 250 oC, which could be transferred to SiO2 without the need of a polymer support. Chapter 3 explores the CVD of tungsten disulphide (WS2) on various substrates including CVD grown graphene. The first example of the AACVD of WS2 onto graphene is reported, where it was shown films as thin as 5 nm could be grown. Using high temperature CVD of tungsten oxide and sulphur, monolayer WS2 was also successfully grown on silicon dioxide and graphene. The characteristic photoluminescent response of monolayer WS2 could be observed on graphene. Materials were analysed using microscopy and spectroscopic techniques such as scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy and powder x-ray diffraction (PXRD). These techniques identified the increased orientation of WS2 deposited onto graphene versus amorphous substrates.Chapter 4 presents findings on how depositing onto graphene substrates may affect the growth and behaviour of tin sulphide materials. Using high temperature CVD, the largest tin sulphide single crystals grown to date from CVD are reported. At lower deposition temperatures, we report the first examples of tin and sulphides deposited onto graphene using an AA-CVD approach. The photoactivity of the tin sulphide-graphene heterostructures has been successfully analysed using photoelectrochemical techniques, where it was found the quality of the graphene substrate had a large effect on device performance. Additionally, bandgaps of the tin sulphides were affected when deposited onto graphene, indicating graphene substrates effect strain in heterostructure materials. As with WS2 depositing onto graphene altered the orientation of tin disulphide, which could be observed by SEM, AFM and PXRD.
|Date of Award||27 Jun 2017|
|Supervisor||Andrew Johnson (Supervisor), Paul Raithby (Supervisor) & Simon Bending (Supervisor)|
Heterostructures from Chemical Vapour Deposition. The Synthesis and Characterisation of Tungsten and Tin Chalcogenides on Graphene Substrates
Rushworth, A. (Author). 27 Jun 2017
Student thesis: Doctoral Thesis › PhD