Molecular Beam Epitaxy of Superconducting (Rb,Ba)BiO sub 3.

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 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 and spotty RHEED patterns are obtained on (1 0 0) MgO substrates, despite the good lattice match for (1 0 0) growth. Both streaked and spotty reflection high energy electron diffraction (RHEED) patterns have been obtained on either substrate. Sticking coefficients for bismuth depend on the growth conditions, indicating that the epitaxy is partially controlled by desorption kinetics. Obscure compounds in the (RbOx,BaO)-Bi2O sub 3 system participate in the epitaxy.