Microstructure and deposition characteristics of κ-Al2O3

The aim of this work is to elucidate the influence of pressure in combination with different degrees of catalysis on the growth and microstructure of chemically vapour deposited (CVD) kappa-Al2O3. The coatings were deposited at 1000 degrees C in a vertical hot-wall reactor. Hydrogen sulphide (H2S) was used as a doping agent. The experimental kappa-Al2O3 coatings were deposited as multilayers and up to 8 layers of kappa-Al2O3 were obtained with different process parameters in the same run. Thin TiN interlayer were deposited to separate the kappa-Al2O3 layers. Growth rates of kappa-Al2O3 as a function of pressure and dopant concentration were measured using scanning electron microscopy (SEM). The changes in the microstructure of the kappa-Al2O3 layers were investigated using transmission electron microscopy (TEM). The growth rate of kappa-Al2O3 could be strongly enhanced by applying H2S doping or by increasing the deposition pressure. kappa-Al2O3 coatings which were deposited at differing process conditions did not exhibit any pronounced microstructural or morphological variations.