PENETRATION DEPTH, MICROWAVE SURFACE-RESISTANCE, AND GAP RATIO IN NBNAND BA1-XKXBIO3 THIN-FILMS

We report values of the zero temperature magnetic penetration depth la mbda(0), microwave surface resistance R(s), and gap ratio 2 Delta(0)/k (B)T(c) in technologically useful thin films of NbN and Ba1-xKxBiO3. A novel analysis technique was used to extract the absolute magnitude o f lambda(0) and 2 Delta(0)/k(B)T(c) from shifts in resonant frequency of a parallel-plate resonator. For NbN and Ba1-xKxBiO3 values of lambd a(0)=3900+/-200 Angstrom and 3300+/-200 Angstrom were obtained, respec tively. The gap ratios were found to be 2 Delta(0)/k(B)T(c)=4.1+/-0.1 and 3.8+/-0.5, respectively, for T-c=16.3 K in NbN and T-c=17.2 K in B a1-xKxBiO3. The surface resistance measurements on Ba1-xKxBiO3 represe nt the lowest values ever reported at microwave frequencies in this ma terial.