Microwave characterization of as-grown MgB/sub 2/ thin films prepared by molecular beam epitaxy

The MgB/sub 2/ superconductor with T/sub C/ of 39 K has great potential to replace some LTS materials in superconducting electronics. Thin films with low surface resistance, (R/sub S/) and negligible nonlinear effects are necessary to realize MgB/sub 2/ circuits for microwave applications. The R/sub S/ of MgB/sub 2/ thin films varies significantly depending on the method of deposition and deposition conditions. We have investigated microwave properties of MgB/sub 2/ thin films grown on MgO substrate by the Molecular Beam Epitaxy method with novel co-evaporation conditions at low deposition rate in ultra-high vacuum. The R/sub S/ of as-grown MgB/sub 2/ thin films have been measured using the Hakki-Coleman Sapphire dielectric resonator technique. High measurement accuracy was accomplished by using multifrequency measurements of S-parameters and the Transmission Mode Q-Factor technique for data processing to obtain the unloaded Q/sub o/-factor and resonant frequency of the dielectric resonator. Measured R/sub s/ of the MgB/sub 2/ films of 400 /spl mu//spl Omega/ was obtained at frequency of 24.6 GHz and temperature of 13 K. Microwave power characteristics of R/sub s/ indicates stable operation of MgB/sub 2/ devices for the input power up to 10 dBm.