Molecular beam epitaxy. A path to novel high T_c superconductors?

The molecular beam epitaxial growth of layered Bi-Sr-Ca-Cu-O films is reported. The advantage of using ozone rather than molecular oxygen for the growth of cuprate superconductors by molecular beam epitaxy (MBE) is discussed. Molecular beams of the constituent metals were shuttered on an atomic layer-by-layer basis to grow Bi₂Sr₂Ca_n-1Cu_nO_x phases for n=1 to 5, and ordered superlattices of these phases. Using these techniques an as-grown superconducting film with T_c^onset near 100 K and T_c (ρ=0) of 84 K was achieved. The films are smooth on an atomic scale. The results demonstrate the ability of shuttered MBE to grow custom layered combinations of Bi₂Sr₂Ca_n-1Cu_nO_x layers. This shuttered MBE growth technique seems quite capable of synthesizing artificially layered epitaxial structures consisting of layers of oxides that are superconducting, non-superconducting metals, semiconducting, or insulating, with control of layer thickness and abruptness on an atomic scale.