  We have grown NdBa2Cu3O7-d films under silver atomic flux by molecular beam
epitaxy, which show a drastic improvement in microstructure and also
crystallinity leading to 30 % enhancement in critical current density. The most
remarkable point is that the final film is free from silver. The key to our
process in achieving a silver-free film was the use of RF-activated oxygen that
oxidizes silver, nonvolatile, to silver oxide, volatile at the deposition
temperature. This process enables one to utilize the beneficial effects of
silver in the growth of oxide films and at the same time ensures that the final
film be free from silver, which is important for high-frequency applications.
This method can be made use in the growth of thin films of other complex oxide
materials.
