Understanding the catalytic effects of H2S on CVD-growth of α-alumina: Thermodynamic gas-phase simulations and density functional theory

The catalytic effect of H2S on the AlCl3/H2/CO2/HCl chemical vapor deposition (CVD) process has been investigated on an atomistic scale. We apply a combined approach with thermodynamic modeling and density functional theory and show that H2S acts as mediator for the oxygenation of the Al-surface which will in turn increase the growth rate of Al2O3. Furthermore we suggest surface terminations for the three investigated surfaces. The oxygen surface is found to be hydrogenated, in agreement with a number of previous works. The aluminum surfaces are Cl-terminated in the studied CVD-process. Furthermore, we find that the AlClO molecule is a reactive transition state molecule which interacts strongly with the aluminum and oxygen surfaces.