Annealing Behavior of Ba sub 2 YCu sub (3+x) O sub (7+y) Thin Films

The annealing behavior of Ba sub 2 YCu sub (3+x) O sub (7+y) films grown by coevaporation of BaF sub 2, Y and Cu on SrTiO sub 3 has been studied as a function of temperature. Upon annealing at temperatures below 800C, the phase forming first is Ba sub 2 YCu sub 4 O sub 8, independent of the starting stoichiometry. Higher temperatures, above approximately 825C are needed for Ba sub 2 YCu sub 3 O sub 7 to crystallize. Attempts to grow ordered intermediate phases between Ba sub 2 YCu sub 3 O sub 7 and Ba sub 2 YCu sub 4 O sub 8 are in progress.