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Thermal bonding between gold and cobalt

Dear readers, may I as a geologist intrude and ask a very basic question? I am trying to coat small spheres of cobalt (20 microns in diameter) with a thin film of gold, such that the spheres become resistant to corrosion in aqueous fluids up to 800 °C. Using a plasma-arc sputterer I deposited a gold-layer of 100 nm thickness onto the spheres, but unfortunately I do not know at which temperature (and how long) one should do the tempering to obtain a good bond between the gold layer and the cobalt sphere. Any advise is greatly acknowledged.

Andreas Audetat
- Tübingen, Germany
2003

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2006

Dear Mr. Audetat,
your requirements are rather harsh for a thinfilm technology! We are concerned with transport processes in micro-dimensioned constructions since decennia and can recommend to apply first a diffusion barrier before Au sputtering. The optimal layer sequence is e.g. Ti-Pt-Au.
yours sincerely,

Dr.-Ing. H. Hieber
ICR - Jena, Germany