VACUUM EVAPORATION OF THIN ALUMINA LAYERS

Amorphous a-Al2O3 thin films were prepared by vapour deposition using a special Knudsen cell heated by electron bombardment. The Al/O stoich iometry was controlled in situ by Auger electron spectroscopy, and the structure by transmission electron microscopy. It is shown that the s toichiometric layers can be prepared at a cell temperature of up to 20 50 K which corresponds to a deposition rate of 3 nm h(-1) at a cell-su bstrate distance of 50 mm. At higher temperatures alumina molecules st art to dissociate and the layers contain free Al atoms. In this case t he stoichiometry of the layers can be improved by evaporation under ox ygen atmosphere.