Particle-free superconducting Bi2Sr2CaCu2Ox ultrathin films prepared by atomic-layer-controlled molecular beam epitaxy technique

Atomic-layer-controlled molecular beam epitaxy (ALC-MBE) technique is applied for preparing Bi₂Sr₂CaCu₂O_x ultrathin films. Precise control of the composition by ALC-MBE enables successful growth of particle-free ultrathin films. Superconducting zero-resistance transitions are observed for the films more than 3.0 nm in thickness. It is also shown that growth of a Bi₂Sr₂CuO_y buffer layer between the film and SrTiO₃(100) substrate contributes to preparing such particle-free ultrathin films with good superconducting properties.