Microstructure and deposition characteristics of κ-Al₂O₃

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