Remote microwave plasma enhanced chemical vapour deposition of alumina on metallic substrates

This paper is devoted to the discussion of insulating aluminium oxide layer s deposited on metallic substrates in the afterglow region of a microwave o xygen plasma. The chosen organometallic precursor, trimethylaluminium (TMA) , has high vapour pressure and reactivity. The experimental set-up is descr ibed and the influence of the deposition parameters on deposition rate, phy sical and chemical properties of the coatings is presented. Deposition rates range from 0.05 to 0.2 mu m min(-1). Microwave power and p ressure ranges are limited by the formation of particles produced by homoge neous nucleation in the gas phase for high values. Weight gain, which illus trates the deposition rate, is strongly dependent on the precursor flow rat e. Density and chemical composition are improved by deposition temperature. The main impurities are CH, groups. High compressive stresses and electric al resistivity are well suited for the planned uses of these coatings at hi gh temperature on turbine blades. (C) 1999 Elsevier Science S.A. All rights reserved.