The adhesion of metallic films to laser-irradiated alumina
- Department of Materials Science and Engineering, The University of Tennessee, Knoxville, Tennessee 37996-2200 (United States)
- Solid State Division, Oak Ridge National Laboratory, P. O. Box 2008, Oak Ridge, Tennessee 37831-6056 (United States)
The adhesion strength of copper and nickel films deposited onto polycrystalline alumina (Al{sub 2}O{sub 3}) substrates is greatly increased by pulsed ultraviolet excimer (XeCl, 308 nm) laser irradiation of the alumina prior to metal-film deposition. Adhesion enhancement occurs for pulsed-laser energy densities, {ital E}{sub {ital d}}, both below and above alumina`s melting threshold ({ital E}{sub {ital d}}{sup th}{similar_to}0.7 J/cm{sup 2}). Cross-section transmission electron micrographs of alumina irradiated at {ital E}{sub {ital d}}{gt} {ital E}{sub {ital d}}{sup th} reveal an outer amorphous layer 40--60 nm thick that is formed during the rapid solidification process that follows pulsed-laser melting. Our results for gold, copper, and nickel films demonstrate that several factors contribute to metal-alumina bonding: (1) the chemical nature of the metal, as indicated by quite different adhesion strengths of sputter-deposited metals on unirradiated alumina substrates: 0.1 MPa for Au, 13 MPa for Cu, and 32 MPa for Ni; (2) the type and extent of laser-generated disorder/damage, since for gold significant bonding enhancement is obtained only if pulsed-laser melting of the alumina occurs; and (3) the irradiation atmosphere, as the adhesion strength of these metals to alumina is greatest if pulsed-laser irradiation is performed in an oxidizing atmosphere.
- OSTI ID:
- 45970
- Journal Information:
- Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 10 Vol. 77; ISSN JAPIAU; ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
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