Atomic-layer-by-layer Molecular Beam Epitaxy Research Articles

Engineering of ultrathin barriers in high T C, trilayer Josephson junctions

Josephson junctions with ultrathin (25–40 Å) barriers were fabricated using high TC, trilayer films grown by atomic layer-by-layer molecular beam epitaxy (ALL-MBE). The films consisted of top and bottom electrodes of Bi2Sr2CaCu2O8, separated by a single molecular layer of a metastable compound, Bi2Sr2(Ca, Sr, Bi, Dy)n−1CunO2n+4, with n=5 to 11. Systematic variation of Bi or Dy doping on Ca sites in the barrier layer provided four orders of magnitude of tuning of both the junction critical current and the normal state resistance, while keeping their product approximately constant, near 0.5 mV. Barrier and junction engineering, on an atomic length scale, has been demonstrated for the first time.

Superconductivity in epitaxial Bi2Sr2CuO6/Bi2Sr2CaCu2O8 superlattices: The superconducting behavior of ultrathin cuprate slabs

Utilizing atomic layer-by-layer molecular beam epitaxy (ALL-MBE), we have synthesized a series of high-quality superlattices in which ultrathin slabs (one-half unit cell thick) of the high-Tc superconductor Bi2Sr2CaCu2O8 alternate with up to five such layers of the low-Tc Bi2Sr2Cu1O6 phase. In all these superlattices we foundTc to be essentially equal to that of the high-Tc Bi2Sr2CaCu2O8 phase itself, which indicates that this cuprate is a 2D superconductor insofar as the interslab coupling plays at best a secondary role. Furthermore, it is demonstrated thatTc need not be reduced at heterostructure interfaces.

Superconducting Multilayer Structures Grown by All-Mbe

ABSTRACTThin films of various Bi-Sr-Ca-Cu-O (2201, 2212,…, 2–2–11–12) compounds have been synthesized using atomic-layer-by-layer molecular beam epitaxy (ALL-MBE). Single-crystal films with excellent transport properties, smooth surfaces and atomically sharp interfaces in multilayer structures have been obtained. That made it possible to deposit virtually perfect ultrathin layers and superlattices, and fabricate hysteretic Josephson junctions from SIS multilayers.