High frequency characterization of high temperature superconductors

A program has been established to develop and characterize thin-film high T/sub c/ superconducting materials for microwave and millimeter-wave applications. Presently, these efforts are focused on the characterization of YBa/sub 2/Cu/sub 3/O/sub x/ and Bi/sub 2/CaSr/sub 2/Cu/sub 2/O/sub r/ thin films, deposited on MgO substrates. A flash evaporation technique has been developed for depositing these materials which produces films with zero resistance critical temperatures in the range of 75 K to 85 K, excellent stoichiometry and alignment, and microwave surface resistances on the order of copper. The technique developed has the advantage of being able to maintain stoichiometry over large substrate areas. For circuit patterning, chemically assisted ion beam etching of superconductors has been developed. Characterization techniques are described. The microwave properties of the superconducting thin films are determined from measurements of the resonance behavior of microstrip, stripline, and cavity resonators.<>