Superconducting (Rb, Ba)BiO sub 3 Thin Films Grown by Molecular Beam Epitaxy.

The simple cubic perovskite (Rb,Ba)BiO sub 3 can be grown by molecular beam epitaxy using an RF plasma atomic oxygen source. Films with superconducting onsets in resistivity as high as 27K are obtained without annealing. The epitaxy proceeds in the normal (1 0 0) orientation on (1 0 0) SrTiO sub 3, despite a 10% lattice mis-match. (1 1 0) epitaxy is obtained on (1 0 0) MgO substrates, despite the good lattice match for (1 0 0) growth. The films with the lowest normal state resistivity are those grown on SrTiO sub 3 at 300+-10C and are Bi deficient despite excess Bi flux during growth. The temperature dependence of the resistivity for these films is metallic down to T sub c. H sub (c2) for a T sub c =20K film is 10+-1T.