Pulsed laser ablation deposition and characterization of superconductive/ferroelectric bilayers

Abstract

Superconductive/ferroelectric YBCO/PZT bilayer structures have been deposited by pulsed laser ablation on (100) MgO and SrTiO 3 substrates. Before the fabrication of the bilayer, optimization of the YBCO deposition parameters was carried out to improve the electrical, morphological and structural characteristics of the films. The results of x-ray diffraction spectroscopy, resistance versus temperature measurements, atomic force and scanning electron microscopies demonstrate the growth of YBCO films suitable as bottom layers for subsequent PZT deposition. The superconductive/ferroelectric bilayers, as characterized by x-ray diffraction and scanning electron microscopy, demonstrate the presence of the correct lattice structures for both YBCO and PZT layers and a good surface morphology (i.e. the absence of cracks and holes and low droplet density). The ferroelectric capacitors realized by using the YBCO layer and evaporated gold dots as bottom and top electrodes, respectively, exhibit excellent ferroelectric behaviour (remanent polarization P r ≈ 21 µC cm −2 , coercive field E c ≈ 100 kV cm −1 ), suggesting that laser deposited YBCO/PZT bilayers are promising as candidates for the fabrication of non-volatile random access memory devices.

Microwave applications of high-temperature superconductors

“…Also the loss tangent of thin film samples may be several orders of magnitude worse than the best bulk samples. These poorly understood sample-dependent effects are at present limiting the use of these potentially very attractive tunable microwave devices [76]. The monolithic phaseshifter discussed above has also allowed resonator tuning to be investigated [59]: the compatibility of YBCO with ferroelectrics other than SrTiO 3 has been attempted.…”