The mechanical properties of alumina films formed by plasma deposition andby ion irradiation of sapphire

This paper examines the correlation between mechanical properties and the d ensity, phase and hydrogen content of deposited alumina layers, and compare s them to those of sapphire and amorphous alumina synthesized through ion-b eam irradiation of sapphire. Alumina films were deposited using electron be am evaporation of aluminum and cobombardment with O-2(+) ions (30-230 eV) f rom an electron-cyclotron resonance (ECR) plasma. The II content and phase were controlled by varying the deposition temperature and the ion energy. S apphire was amorphized at 84 K by irradiation with Al and O ions (in stoich iometric ratio) to a defect level of 4 dpa in order to form an amorphous la yer 370 nm thick. Nanoindentation was performed to determine the elastic mo dulus, yield strength and hardness of all materials. Sapphire and amorphize d sapphire have a higher density and exhibit superior mechanical properties in comparison to the deposited alumina films. Density was determined to be the primary factor affecting the mechanical properties, which showed only a weak correlation to the hydrogen content. (C) 2000 Published by Elsevier Science B.V. All rights reserved.