We have grown Nd Ba2 Cu3 O7-δ films under silver atomic flux by molecular-beam epitaxy, which show a drastic improvement in microstructure and also crystallinity leading to a 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 used in the growth of thin films of other complex oxide materials.
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