Superconductors and Insulators in Rubidium Barium Bismuth Oxide Films Grown In-Situ by Molecular Beam Epitaxy

Investigations of epitaxial growth in the rubidium barium bismuth oxide material system have shown it to be an powerful synthetic technique. The simple cubic perovskite (Rb,Ba)BiO sub 3 can be grown at temperatures below 350C by molecular beam epitaxy using an RF plasma atomic oxygen source. Films with metallic normal state conductivity and superconducting onsets in resistivity as high as 27K are obtained without annealing. The epitaxy proceeds in the normal (100) orientation on (100) SrTiO sub 3, despite a 10% lattice mismatch. (110) epitaxy is obtained on (100) MgO substrates, despite the good lattice match for (100) growth.