Simulating growth of a diamond film by CVD

This example computes the growth rate of a diamond film according to a simplified version of a particular published growth mechanism (see file diamond.yaml for details). Only the surface coverage equations are solved here; the gas composition is fixed. (For an example of coupled gas-phase and surface, see catcomb.m).

Atomic hydrogen plays an important role in diamond CVD, and this example computes the growth rate and surface coverages as a function of [H] at the surface for fixed temperature and [CH3].

Requires: cantera >= 2.6.0, pandas >= 0.25.0, matplotlib >= 2.0

Tags: Matlab surface chemistry kinetics

Initialization

clear all
close all

help diamond_cvd
t0 = cputime; % record the starting time

Operation Parameters

t = 1200.0; % surface temperature
p = 20.0 * OneAtm / 760.0; % pressure

Create the gas object

The gas phase will be taken from the definition of phase ‘gas’ in input file ‘diamond.yaml’.

gas = Solution('diamond.yaml', 'gas');
gas.TP = {t, p};
x = gas.X;
ih = gas.speciesIndex('H');
xh0 = x(ih);

Create the bulk diamond object

The bulk phase will be taken from the definition of phase ‘diamond’ in input file ‘diamond.yaml’.

dbulk = Solution('diamond.yaml', 'diamond');
mw = dbulk.molecularWeights;

Create the interface object

This object will be used to evaluate all surface chemical production rates. It will be created from the interface definition ‘diamond_100’ in input file ‘diamond.yaml’.

surf_phase = Interface('diamond.yaml', 'diamond_100', gas, dbulk);

Advance Coverages

iC = surf_phase.kineticsSpeciesIndex('C(d)');

xx = [];
rr = [];
cov = [];

for i = 1:20
    x(ih) = x(ih) / 1.4;
    gas.TPX = {t, p, x};
    surf_phase.advanceCoverages(10.0);
    r = surf_phase.netProdRates;
    carbon_dot = r(iC);
    mdot = mw * carbon_dot;
    rate = mdot / dbulk.D;
    xx = [xx; x(ih)];
    rr = [rr; rate * 1.0e6 * 3600.0];
    cov = [cov; surf_phase.coverages];
end

Make Plots

clf;

subplot(1, 2, 1);
plot(xx, rr);
xlabel('H Mole Fraction');
ylabel('Growth Rate (microns/hr)');
title('Growth Rate');

subplot(1, 2, 2);
plot(xx, cov);
xlabel('H Mole Fraction');
ylabel('Coverage');
title('Coverages');