Superconducting properties of ultrathin films of YBa₂Cu₃O_x prepared by metalorganic chemical vapor deposition at 500°c

Low-temperature (500°C) growth of YBa₂Cu₃O_x films by metaloganic chemical vapor deposition on (100)MgO substrates using N₂O as an oxidizing agent has been investigated. Films 12 unit cells thick show superconducting onset critical temperature of 89 K and zero-resistivity critical temperature of 80 K. Films 4 unit cells thick show T_c (zero) of 30 K. Films as thin as 3 unit cells thick reveal superconducting onset characteristics. If the topmost (cap) layer and the bottom (buffer) layer are nonsuperconducting, this result suggests that superconductivity arises even from monomolecular layer of YBa₂Cu₃O_x.