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.