Influence of the current applied to the silver target on the structure and the properties of Ag-Cu-O films deposited by reactive cosputtering

Ag-Cu-O films were deposited on glass substrates by reactive magnetron cosputtering of silver and copper targets. In this manuscript, the current applied to the copper target and the oxygen flow rate introduced into the deposition chamber were kept constant, whereas the current applied to the silver target (IAg) was varied. Films deposited without silver crystallised into the paramelaconite structure (Cu4O3). At low silver target current, incorporation of Ag into Cu4O3-based did not modify the film structure. Silver atoms substituted some Cu(+I) atoms leading to the formula: Ag2−xCu2+xO3. On the other hand, when IAg exceeded a critical value, X-ray diffraction analyses revealed a biphased structure: Ag2−xCu2+xO3 and Ag. Contrary to the diffraction peak intensity of the Ag2−xCu2+xO3 phase, that of silver was increased with IAg. For the highest value of IAg, no silver-copper oxide was detected and the mean crystal size of silver grains was close to 2 nm. Due to the occurrence of the nanocrystallised silver phase, the film electrical resistivity strongly decreased. Optical reflectance measurements confirmed the structural changes versus the silver target current.