Large area RE-123 thin films for microwave applications grown by molecular beam epitaxy

Abstract Many microwave applications of high temperature superconductors require double-sided films on substrates with diameters larger than 2 inches. Although there are different techniques for the growth of fair quality superconductor films, there exists a need for further improvement in quality, uniformity, reproducibility and scalability in order to meet the commercial requirements for RF device applications. We have succeeded in growing high quality RE-123 (RE=Nd, Dy, Eu) films by molecular beam epitaxy (MBE). In general, MBE growth of high temperature superconductor films requires strict compositional control and strong, yet controllable, oxidation. By optimizing the growth parameters, we have grown excellent quality RE-123 films on (1 0 0) MgO. Nd-123 films grown on MgO under optimized conditions gave a T C (0) of 94 K with a room temperature resistivity of ∼200 μΩ  cm and a J C of ∼ 3.5 MA/cm 2 at 77 K. The films had excellent metallicity and were in-plane aligned. The MBE grown RE-123 films were characterised by low microwave surface resistance values. Best R S values of Nd-123 films on MgO were 890 μΩ at 77 K and below 100 μΩ at 20 K at 22 GHz. Microstrip bandpass filters fabricated using MBE grown Nd-123 films yielded higher IP3 values than the one made from commercially available Y-123 films indicating the better power handling capability of MBE grown Nd-123 films.