Composition–constitution–morphology relationship of Al2O3 thin films deposited by plasma assisted chemical vapor deposition

We have studied the correlation between the chemical composition, constitution and morphology of Al2O3 using experimental and theoretical means. Combining scanning electron microscopy, transmission electron microscopy, electron dispersive X-ray analysis and ab initio calculations, we have investigated the formation of pores. Desorption measurements show chlorine release from γ- and α-alumina films. Based on ab initio calculations, we have established that Cl can be incorporated in both γ- and α-alumina. Furthermore, two Cl atoms are likely to agglomerate since the total energy is reduced, compared to an unagglomerated configuration. We propose that Cl agglomeration is the first step towards Cl2 formation and subsequent precipitation and bubble formation. It can be learned that the Cl incorporation has to be minimized during growth of dense alumina coatings.