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.