Three-dimensional kinetic Monte Carlo simulations of diamond chemical vapor deposition

Abstract

A three-dimensional kinetic Monte Carlo model has been developed to simulate the chemical vapor deposition of a diamond (100) surface under conditions used to grow single-crystal diamond (SCD), microcrystalline diamond (MCD), nanocrystalline diamond (NCD), and ultrananocrystalline diamond (UNCD) films. The model includes adsorption of CH x (x = 0, 3) species, insertion of CH y ( y = 0-2) into surface dimer bonds, etching/desorption of both transient adsorbed species and lattice sidewalls, lattice incorporation, and surface migration but not defect formation or renucleation processes. A value of ∼200 kJ mol −1 for the activation Gibbs energy, ∆G ‡ etch , for etching an adsorbed CH x species reproduces the experimental growth rate accurately. SCD and MCD growths are dominated by migration and step-edge growth, whereas in NCD and UNCD growths, migration is less and species nucleate where they land. Etching of species from the lattice sidewalls has been modelled as a function of geometry and the number of bonded neighbors of each species. Choice of appropriate parameters for the relative decrease in etch rate as a function of number of neighbors allows flat-bottomed etch pits and/or sharp-pointed etch pits to be simulated, which resemble those seen when etching diamond in H 2 or O 2 atmospheres. Simulation of surface defects using unetchable, immobile species reproduces other observed growth phenomena, such as needles and hillocks. The critical nucleus for new layer growth is 2 adjacent surface carbons, irrespective of the growth regime. We conclude that twinning and formation of multiple grains rather than pristine single-crystals may be a result of misoriented growth islands merging, with each island forming a grain, rather than renucleation caused by an adsorbing defect species. C 2015 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License. [http://dx

Etching Kinetics of (100) Single Crystal Diamond Surfaces in a Hydrogen Microwave Plasma, Studied with In Situ Low‐Coherence Interferometry

“…Following to Ivanov et al this may indicate that the etched C d H 2 molecules are probably adjacent to other C d H 2 units on a flat face, and that its removal requires a higher energy to break C–C bonds. We can add to this information that the activation energy of 48 kcal mol −1 was deduced the kinetic Monte Carlo modeling of diamond growth, while recently, Glowacki et al modeled CH 3 dissociation from the diamond surface by molecular dynamics (MD) simulations found the free energy of activation of 35 kCal mol −1 for CH 3 dissociation at the diamond surface. Our measured activation energies seem to be in agreement with those two recent calculations.…”

What [plasma used for growing] diamond can shine like flame?

“…Diamond growth occurs at the gas-surface interface, and it is fair to note that there is still much work required to determine the extent of gas processing in the boundary layer immediately above the growing surface, and in the larger scale simulation of diamond growth from the gas phase. [125][126][127] Another valid question is the extent to which all the foregoing plasma chemical insights could be used to enhance the efficiency of the diamond CVD process. Efficiency can be assessed in several ways.…”

Reaction and relaxation at surface hotspots: using molecular dynamics and the energy-grained master equation to describe diamond etching

“…In a recent kinetic Monte Carlo modelling study of diamond growth under CVD conditions [37], it was found that good agreement with observed rates of growth could be found when assuming a rate constant for etching provided with an Eyring expression together with a temperature-independent free energy of activation of 200 kJ mol −1 (48 kcal mol −1 ). While this is larger than the values shown in table 5, it should be noted that this value in fact corresponds to the activation free energy for loss of an adsorbed ‘carbon’, which is typically present as a ─CH 2 group inserted into a surface C–C bond.…”