EFFECT OF H_2S ON THE MICROSTRUCTURE AND DEPOSITION CHARACTERISTICS OF CHEMICALLY VAPOUR DEPOSITED A1_2O_3

摘要

The influence of experimental variables in combination with catalysis on the growth and microstructure of CVD K-Al_2O_3 was investigated. The Al_2O_3 coatings were deposited in the temperature range of 800-1000°C and at pressures of 50 to 400 mbar. Hydrogen sulphide (H_2S) was used as a doping/catalysing agent. General deposition characteristics of K-Al_2O_3 as a function of temperature, pressure and H_2S concentration are reported. In general, K-Al_2O_3 deposited at different process conditions did not exhibit any pronounced microstructural or morphological differences. However, at deposition temperature of 800°C together with higher doping levels (H_2S>0.8%) γ-Al_2O_3 was obtained. Enrichment of sulphur could be confirmed to occur inγ-Al_2O_3 while no sulphur was found in K-A1_2O_3.