Publications Details
Effect of O{sub 2} partial pressure on post annealed Ba{sub 2}YCu{sub 3}O{sub 7-{delta}} thin films
Epitaxial films of Ba{sub 2}YCu{sub 3}O{sub 7-{delta}} (BYCO) as thin as 250 {Angstrom} and with J{sub c}`s approaching those of the best in situ grown films can be formed by co-evaporating BaF{sub 2}, Y, and Cu followed by a two-stage anneal. High quality films of these thicknesses become possible if low oxygen partial pressure [p(O{sub 2}) = 4.3 Torr] is used during the high temperature portion of the anneal (T{sub a}). The BYCO melt line is the upper limit for T{sub a}. The use of low p(O{sub 2}) shifts the window for stable BYCO film growth to lower temperature, which allows the formation of smooth films with greater microstructural disorder than is found in films grown in p(O{sub 2}) = 740 Torr at higher T{sub a}. The best films annealed in p(O{sub 2}) = 4.3 Torr have J{sub c} values a factor of four higher than do comparable films annealed in p(O{sub 2}) = 740 Torr. The relationship between the T{sub a} required to grow films with the strongest pinning force and p(O{sub 2}) is log [p(O{sub 2})] {proportional_to} T{sub a}{minus}{sup 1a} independent of growth method (in situ or ex situ) over a range of five orders of magnitude of p(O{sub 2}).