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Title: Theoretical modelling of epitaxial graphene growth on the Ir(111)surface
Author: Tetlow, Holly Alexandra
ISNI:       0000 0004 6062 0498
Awarding Body: King's College London
Current Institution: King's College London (University of London)
Date of Award: 2017
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The main problem aecting the widespread use of graphene based products is the ability to produce high quality graphene in large quantities. One possible method of achieving this is to grow it epitaxially. In this thesis a selection of the important processes involved in epitaxial graphene growth are studied in detail using density functional theory based calculations. It begins with an investigation into the initial stages of the growth process, specically determining the kinetics of the decomposition of ethylene on the Ir(111) surface, in order to nd the decomposition mechanism and the resulting carbon feedstock species that will go on to form graphene. To achieve this the energy barriers of the relevant reactions are determined using the nudged elastic band (NEB) method, and then the reaction kinetics are modelled using both rate equations and a specically developed kinetic Monte Carlo code. The decomposition is determined for a variety of dierent experimental conditions, including temperature programmed growth and chemical vapour deposition. Broadly the results show that the decomposition mechanism involves the breaking of the C-C bond, resulting in the production of C monomers. Following from this the nucleation of carbon clusters on the Ir(111) surface from C monomers prior to graphene formation is investigated. The full, temperature dependent work of formation is devised and calculated for a variety of dierent cluster types. From this value it is possible to determine the critical cluster size, where the addition and removal of C monomers is equally likely. Based on this, small arch-shaped clusters containing four to six C atoms are predicted to be long-lived on the surface, suggesting that they may be key in graphene formation. Finally the healing of single vacancy defects in graphene on the Ir(111) surface is examined. These defects are undesirable and negatively aect the useful properties of graphene. The attempted healing of the defects by ethylene molecules is simulated with molecular dynamics and used to predict partially healed structures. The energy barriers to the healing are determined using NEB calculations. The results suggest that the vacancy defects can be healed directly by dosing with ethylene molecules during graphene growth.
Supervisor: Bonini, Nicola ; Kantorovitch, Lev Nohimovich Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available