Processing and phase stability of metal carboxylate-derived barium-yttrium-copper oxide thin films
The processing and phase stability of Ba$\sb2$YCu$\sb3$O$\sb{\rm 7-x}$ High T$\sb{\rm c}$ thin films are seen to be critical aspects of the successful fabrication of this material. Metal neodecanoates of barium, yttrium, and copper were synthesized and mixed into a homogeneous, precipitate-free solution, which was spin-cast onto ZrO$\sb2$ coated silicon wafers. A minimum heat treated temperature of 725$\sp\circ$C in N$\sb2$ was needed to decompose the BaCO$\sb3$ present in the films. A phase map of the stability of Ba$\sb2$YCu$\sb3$O$\sb{\rm 7-x}$ as a function of heat treatment temperature and ambient showed both the upper and lower temperature boundaries to increase with decreasing P$\sb{\rm O2}$, with the higher temperature boundary truncated at temperatures $>$800$\sp\circ$C from interdiffusion of the films with the substrate. The high temperature decomposition mechanism for the high P$\sb{\rm O2}$ condition was seen to be nucleation of BaCuO$\sb2$, followed by formation of BaY$\sb2$CuO$\sb5$, the accelerated formation of which was attributed to the small grain size ($$90 K was accounted for by the presence of the weak links in the film microstructure.
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign