Masters Theses

Date of Award

12-1994

Degree Type

Thesis

Degree Name

Master of Science

Major

Metallurgical Engineering

Major Professor

Anthony J. Pedraza

Committee Members

D.H. Lowndes, R. Benson

Abstract

The effects of pulsed excimer-laser irradiation prior to film deposition on the adhesion strength of gold, nickel or copper films sputter deposited onto polished polycrystalline alumina substrates and high purity amorphous fused silica have been studied. The effects of oxygen content of the laser irradiation atmosphere as well as the effects of thermal annealing of the metal-ceramic couples following film deposition also have been investigated. The adhesion strengths thus obtained have been correlated with scanning electron microscopy (SEM). The stability of thin films. annealed at high temperatures was investigated using in-situ resistivity measurements. Adhesion enhancement of gold- alumina couples has been obtained for laser energy densities both above and below the melting threshold for alumina. The adhesion strength that results from alumina at these energy levels is associated here with the surface damage that the photo-induced sputtering generates. It is proposed that, owing to the damage, the gold or nickel atoms arriving at the surface can find bonding sites. [1] Post-deposition annealing. is required for further bonding enhancement, suggesting that further rearrangement of the gold and nickel and/or oxygen and aluminum must take place to attain bonding configurations. These results are similar to those obtained by other authors in sapphire specimens sputtered with 500 eV Ar+ ions prior to deposition of copper films.[2] Fused silica, which unlike alumina is a more covalently bonded ceramic, shows different results with respect to adhesion enhancement. It does not exhibit the dramatic improvement in adhesion found with alumina, nor does it show the strikingly similar functional dependence of adhesion strength on laser energy density as obtained with alumina-gold couples. However, ablation seems to have a deleterious effect on the adhesion strength in the cases of both fused silica and alumina. It is probable that ablation removes some of the favorable conditions created for bonding by laser. melting and solidification, thus accounting for decrease in adhesion strength for energy densities greater than the ablation threshold.

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