Synthesis of a-axis-oriented AlN film by a shielded reactive vacuum are deposition method

Aluminum nitride (AlN) thin films were fabricated by a non-shielded conventional reactive vacuum are deposition method and by a shielded vacuum are deposition method in which a droplet-shielding plate was located between the cathode and substrate. The properties of the films, such as surface morphology, number of droplets, deposition rate, crystalline structure, optical properties, hardness, and elastic modulus were investigated. The films deposited by the non-shielded method were metallic silver, very rough due to many macrodroplets, and easily peeled off from the substrate, whereas the films deposited by the shielded method were transparent in the visual and near-infra-red regions, smooth and almost droplet-free, and adhered well. The former exhibited a c-axis orientation, whilst the latter showed a-axis orientation. The refractive indices of the films deposited by the shielded method were 1.9-2.1, and the extinction coefficients were less than 10(-2). The films were much harder and stiffer than boro-silicated glass. (C) 1999 Published by Elsevier Science S.A. All rights reserved.