Study of copper on graphite with titanium or chromium bond layer

Improvement of copper to graphite adhesion by thin interfacial films of titanium and chromium was investigated. Graphite fibers and highly oriented pyrolytic graphite flats were sputter-coated first with 10 nm of titanium or chromium and then with 50 nm of copper. After annealing to 970 °C in argon/5%-hydrogen at atmospheric pressure for 5 min, copper without an interfacial bond layer agglomerated into nearly spherical particles, copper with the chromium bond layer agglomerated into particles with a contact angle less than 90°, indicating improvement in adhesion, and copper with the titanium bond layer exhibited a continuous metal film. In the latter case, most of the interfacial titanium was observed to have migrated into the copper and to the free surface, where the titanium reacted with contaminants in the annealing ambient.