Integrated Ferroelectric and Superconductor Concept for Device Applications

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The high temperature superconductor, BiCaSrCu-oxide, and the ferroelectric Bi4Ti3O12 have orthorhombic lattice constants that match almost exactly. Single crystals of the Bi-ferroelectric are available in the form of large thin plates where the long axis of the unit cell is perpendicular to the plate, and thin/thick films of the Bi-superconductor can be grown by liquid phase epitaxy. This research deals with an integrated ferroelectric + superconductor structure wherein a film of the Bi-superconductor is grown on a crystal plate of the Bi- ferroelectric. The utility of this approach is that the piezoelectric stress induced in the ferroelectric plate by an applied voltage is used to alter the properties of the superconducting film in the a-b plane for device applications. Measurements of these stress effects on the superconducting transition temperature and critical current density are proposed and anisotropic couplings using actual integrated structures. Magnetic-field effects will also be studied (i.e., magnetic field parallel and perpendicular to the current direction in the film). Lastly, device applications suggested by the measurements will be evaluated.