Copper cladding on polymer surfaces by ionization-assisted deposition

Copper thin films were prepared on poly(ethylene terephthalate) (PET) and polyimide (PI) substrates by an ionization-assisted vapor deposition method. The films had a polycrystalline structure, and their crystallite size decreased with increasing ion acceleration voltage V-a. Ion acceleration was effective in reducing the surface roughness of the films. Cross-sectional transmission electron microscopy revealed that the copper/polymer interface showed increased corrugation with increasing V-a. The increase in V-a also induced the chemical modification of polymer chains of the PET substrate, but the PI substrate underwent smaller modification after ion bombardment. Most importantly, the adhesion strength between the copper film and the PETsubstrate increased with increasing V-a. It was concluded that ionization-assisted deposition is a promising technique for preparing metal clad layers on flexible polymer substrates. (C) 2018 The Japan Society of Applied Physics