OPTIMAL OXYGENATION OF YSR2CU2.75MO0.25OZ THIN-FILMS

Results are presented on the optimization of oxygen content and order in YSr2Cu2.75Mo0.25Oz (YSCMO) thin films. It is shown that due to the high vapor pressure of the chain oxygen of this doped cuprate, optimal oxygenation cannot be achieved through annealing in O-2 at 1 atm. Opt imization of oxygen content can be accomplished globally by ozone anne als at 1 arm, and locally, in thin film microbridges, by electromigrat ion of chain oxygen vacancies out of the microbridges. Both techniques lead to a maximal T-c of 75 K, substantially higher than has been pre viously achieved in this material. The strong correlation between the enhancement in superconducting and normal state properties, and improv ements in oxygen content has been verified by micro-Raman spectroscopy . These results suggest that YSr2Cu3-xMxOz materials in general may be substantially under-oxidized if annealed in O-2 at less than extremel y high pressure, or without some other means that can overcome a compa ratively high chain-oxygen vapor pressure at typical annealing tempera tures. This could affect the interpretation of previous experiments wi th doped cuprate superconductors. (C) 1998 Elsevier Science B.V.