Modelling {100} CVD Diamond Growth Using Kinetic Monte Carlo

Abstract

In this thesis we describe the development of a kinetic Monte Carlo model for the growth of diamond using chemical vapour deposition. The implemented growth model, which can simulate minutes of growth for systems of more than 10,000 carbons, is parametrised by growth-condition inputs taken from detailed modelling and experiment. It is the first of its kind to include the rapid etching of isolated species in combination with CHx migration. The bespoke FORTRAN simulation framework is used to investigate the accuracy of the implemented gas-surface reactions and the kinetics of potential growth mechanisms.

In the first part of this thesis, the model was benchmarked and parametrised with reference to theoretical and experimental literature. An energy barrier to isolated-carbon etching of approximately 35 kJ mol−1, which produced realistic growth behaviour, was in agreement with quantum mechanical calculations. Predictions of growth rates and film roughness as a function of growth condition were largely in agreement with theoretical and experimental literature, although behaviour under microwave-reactor conditions suggested the approximated concentrations of CHx, H or H2 species were inaccurate, or that 2-carbon species play a key role in growth. The formation of deep {111} facets indicate that trough incorporation mechanisms require further investigation.

In the second part of this thesis, the underlying mechanisms behind the observed formation of domains of aligned C–C dimers on the hydrogenated {100} surface were investigated. Passive alignment of forming dimers, driven by favourable energetics had no effect on long-range alignment; the concentration of adjacent carbon radicals was too low. Etching of dimers isolated on the surface also had no effect on alignment, or the formation of domains of dimers. The inclusion of both isolated-carbon and isolated-dimer etching processes together resulted in the reduction of surface pits, although growth-rate predictions were reduced, below those seen in experiment.

The simulation platform and implemented growth model offers powerful atomic-scale analysis and investigation of potential mechanisms leading to defect formation, the incorporation of 2-carbon species (C2H2, C2) and the growth enhancement facilitated by the introduction of N2 species.

Date of Award	22 Mar 2022
Original language	English
Awarding Institution	University of Bristol
Sponsors	IIa Technologies & EPSRC Centre for Doctoral Training in Diamond Science and Technology
Supervisor	Paul W May (Supervisor) & Neil L Allan (Supervisor)