PROPERTIES OF ALUMINA FILMS PREPARED BY METAL-ORGANIC CHEMICAL-VAPOR-DEPOSITION AT ATMOSPHERIC-PRESSURE IN THE PRESENCE OF SMALL AMOUNTS OFWATER

Thin alumina films were deposited on stainless steel, type AISI 304. T he deposition process was carried out in nitrogen with low partial pre ssures of water (0-2.6 x 10(-2) kPa (0-0.20 mmHg)) by metal-organic ch emical vapour deposition (MOCVD) with aluminium-tri-sec-butoxide (ATSB ) as the precursor. Also results are presented regarding the alumina d eposition in the presence of small amounts of 2-butanol. The film prop erties, including the protection of the underlying substrate against a ggressive gas compounds such as sulphur at high temperatures, the chem ical composition, the microstructure, and the refractive index were in vestigated as a function of the water vapour pressure. In contrast wit h the results of stress reduction in silica films by the addition of s mall amounts of water to the deposition process, no significant effect on the internal stress in alumina films was found. TEM analysis showe d that extremely fine grains of gamma-Al2O3/AlO(OH) were formed, in ag reement with the refractive index. Only an increase of the OH groups w as found if water was added to the process, which also was the only im purity in the oxide film. Carbon was not detected.