Effect of ozone anneals on YBa2Cu3-xCoxOz thin films

We report on the effect of 200-500C ozone anneals on the resistivity versus temperature (RT) and Raman spectra characteristics of YBa2Cu3-xCoxOz (Co-Y BCO) thin films, with x=0.3, 0.5, 0.75, and 1.0. Cold wail anneals are cond ucted at similar to 1 atm, of a flowing O-2/O-3 mixture with similar to 2% O-3 by weight. The enhanced partial pressure of atomic oxygen, relative to canonical O-2 anneals, provided by ozone to the surface of Co-YBCO films, l eads to enhanced oxygenation. This is demonstrated by the observation of an increase in T-c (25K to 75K for x=0.3, 0 to 38K for x = 0.5, and 0 to a T- c(onset) of 19K for x=0.75) and improvement in Raman spectra data following ozone anneals. This high degree of oxygenation is unstable under O-2 annea ls at temperatures as low as 200C, We attribute this to the fact that the p artial pressure of oxygen above well oxygenated Co-YBCO is greater than 1 a tm, at similar to 200C. We will discuss the implication of these results fo r the stability and uniformity of SNS ramp edge Josephson junctions which e mploy Co-YBCO N-layers.