FORMATION OF ALUMINUM NITRIDES IN THERMAL PLASMAS

Aluminum nitride has been synthesized by evaporation of the aluminum anode of a free-burning atmospheric-pressure nitrogen arc. About 40% of the product was collected in the form of highly oriented polycrystalline aluminum nitride (from the gaseous phase) with a high deposition rate (almost-equal-to 1-mu-m/s) and very low oxygen content (0.34%). The rest was deposited on the reactor walls as an ultrafine powder with an average particle diameter of 300 angstrom. Destructive and nondestructive tests on the powder and crystals were carried out to determine the morphology and purity of the materials. The impact of other gases on the AlN formation has been studied. The probable mechanism in the AlN crystal growth is discussed.