GREATLY IMPROVED ADHESION OF GOLD-FILMS SPUTTER-DEPOSITED ON LASER-TREATED AND THERMALLY ANNEALED ALUMINA

The effects on adhesion strength of pulsed-laser irradiation prior to film deposition, and of thermal annealing following film deposition, have been studied for gold films deposited by ion beam sputtering on polished polycrystalline alumina [formula ommited] substrates. Three different atmospheres were employed for the laser irradiations: Ar-4% [formula ommited] air, and oxygen, all at 1 atmosphere pressure. A similar functional dependence of adhesion strength on laser energy density, [formula ommited] was found for all of the gaseous environments: No change of adhesion strength for [formula ommited] maximum adhesion for [formula ommited] and decreased adhesion for higher [formula ommited] A pronounced increase in gold-alumina adhesion strength was achieved when the alumina substrates were irradiated in an oxygen-rich atmosphere. A post-deposition 300 °C anneal doubled the adhesion strength to ∼50 MPa, approximately 500 times the strength of untreated gold-alumina couples. The adhesion strength initially increased rapidly with annealing time but saturated for times ⩾ 1 hour. The adhesion enhancement can be attributed to the formation of a high-energy disordered alumina surface during rapid solidification following pulsed-laser melting of the near-surface region. This defective surface contains reactive sites where gold atoms can form strong bonds. The data show that these sites most effectively bond gold atoms when they are saturated with oxygen. © 1995, American Institute of Physics. All rights reserved.