"Multilayer epitaxial heterostructures of high-temperature superconductors of the ReBCO type"

Summary

Complicated crystal structure and anisotropy of physical properties of the high critical temperature superconductors (HTSC) makes difficult reproducible fabrication of the multilayered epitaxial heterostructures of HTSC with necessary parameters. Preparation of normal metal - HTSC and HTSC-HTSC junctions with high parameters reproducibility, especially in multilayer heterostructures with more than one HTSC layer, remains a challenging task instead of more than 10 years of technological investigations. Such structures, though, are necessary both for studies of fundamental HTSC properties and for fabrication of devices of superconducting electronics. The goal of this project is study of growth and formation of the multilayer epitaxial heterostructures of HTSC of the ReBa₂Cu₃O_x family (ReBCO, where Re is the rare earth element). A set of test multilayer heterostructures will be prepared to investigate the electrophysical properties of the heterostructures interfaces and their reproducibility.

Project objectives

The following structures will be prepared and studied:

• multilayer heterostructures metal-HTSC with low contact resistance between layers;

• antennas and resonators with metallisation of the HTSC thin film surface;

• multilayer epitaxial heterostructures with more than one HTSC layer and with an insulator layer providing conditions for epitaxial growth of the HTSC thin film on top of it;

• multilayer epitaxial heterostructures with a screening HTSC layer;

• multilayer epitaxial heterostructures with the interlayer HTSC-HTSC junctions both with and without the weak link formation.

The goals of the project would be achieved by: 1) implementation of new materials and new combinations of materials; 2) application of new technological processes, including utilisation of the substrates with surface plane tilted from the main crystallografic planes; 3) careful step-by-step optimisation of the fabrication processes. Special attention will be paid to the reproducibility of the obtained structures, along the sample surface and from sample to sample. The first steps for incorporation of the developed technological processes into a fabrication procedure for preparation of complicated HTSC structures will be done.

Group activity - 2001

During the first year of the project the bottom layers of the superconducting heterostructure should be developed. These are the screening HTSC layer and the insulator layer; both layers must provide possibility of epitaxial growth of the higher HTSC layers and a smooth surface (roughness R_a less than 3 nm, density of particles less than 10⁶ cm^-2).