High performance YBCO films. Report for 1 December 1993-25 February 1994

A program plan for Phase III of the contract was submitted and approved. It incorporates a silver capping layer and a glass/metal handle for support of a thin YBCO/magnesium fluoride microstrip structure. The basic technology can be applied to MCM's as well as millimeter wave circuit needs. A silver capping layer of thickness 5 microns was found to be compatible with glass and able to withstand processing temperatures of 550 C used for firing and annealing of the glass. However, after subjecting the silver/glass combination to 700 C (to simulate the effect of depositing a subsequent YBCO signal layer in the complete MCM structure), there was some degradation in the silver's conductivity as measured using the dielectric resonator technique. A thicker silver layer is apparently needed to adjust for the interfacial reaction between the silver and the glass. Silver was deposited on both STO and YBCO-covered samples with excellent adhesion. After heating the samples to 750C in flowing nitrogen, the adhesion of the silver remained excellent when tested with scotch tape.