Oxide heterostructures

Multilayer high-temperature superconductor flux transformers

Multilayer thin film epitaxial high-T_c superconducting flux transformers developed for implementation in flip-chip magnetometers and gradiometers to improve their sensitivity to about 2 fT/rt(Hz) and 15 fT/cm.rt(Hz) respectively.

1. M. I. Faley et al., IEEE Transactions on Appl. Supercond. 11 (1), 1383 (2001).
2. M. I. Faley et al., IEEE Transactions on Appl. Supercond. 28 (4) 1600505 (2018).

Multilayer buffer for high-temperature superconductor devices on MgO substrates

A multilayer thin film epitaxial passivation of single crystal MgO substrates was developed. YBa₂Cu₃O_7−x films on the buffered MgO substrates demonstrate pure c-axis orientation, absence of in-plane disoriented grains, transition temperature 91 K, and critical current density 5 MA/cm² at 77.4 K and were deposited in thicknesses of up to several micrometers without cracks. High-temperature superconductor multilayer flux transformers of 2 µm thickness on the buffered MgO substrates demonstrated improved insulation between the superconducting layers and an increased dynamic range compared to flux transformers on SrTiO₃ substrates.

1. M. I. Faley et al., Appl. Phys. Lett. 89, 082507 (2006).
2. S.B.Mi et al., J. Crystal Growth 300 478 (2007).

Resistive switching devices with superconducting electrodes

Electron transport properties and microstructure of an interface between YBa₂Cu₃O_7-x (YBCO) and SrTiO₃ (STO) in thin film heterostructures YBCO/STO/Al/Pt on STO and MgO substrates were investigated. A resistance switching ratio over 1000 and a stable operational endurance over 5000 cycles were observed at room temperature. A local dependence of Schottky barrier height on the resistive state of the cell was detected using EBIC (Electron-Beam-Induced-Current) system (Point Electronic GmbH) installed at JEOL 7400F scanning electron microscope. Time dependence of the retention characteristics of low resistive state obeys Curie-von-Schweidler behaviour with the exponent 0.35 which indicates on the lowering the Schottky barrier due to a charge trapping. The observed ideality factor n approximately 6.7 indicates on the significance of the interfacial layer for the resistive switching effect. A model applicable for the explanation of the resistive switching effect at YBCO/STO interface and based on modulation of the electron affinity of STO layer is proposed. Our findings can be used for development of the prospective nanoscale resistive switching devices.

1. M. I. Faley et al.,
   "New prospective applications of heterostructures with YBa₂Cu₃O_7-x".
   Chapter 5 in book “Superconductors - new developments”,
   ISBN 978-953-51-2133-6, Edited by A. Gabovich, Rijeka: InTech; pp. 73-94 (2015).

Nanofabrication and Quantum Sensing

Prof. Dr. Michael Faley

Phone: +49 2461 61-4366
Fax: +49 2461 61-6444
E-Mail: m.faley@fz-juelich.de