Substrates for high-T_csuperconductor microwave integrated circuits

TLDR

The review outlines substrate properties essential for YBa₂Cu₃O₇‑x thin‑film quality and microwave circuit design, emphasizing lattice match, thermal expansion compatibility, chemical stability, absence of twinning, dielectric permittivity, loss tangent, and required substrate area. The paper reviews dielectric substrate materials suitable for YBa₂Cu₃O₇‑x thin‑film microwave integrated circuits and specifies the required substrate properties. The authors discuss dielectric substrate materials for YBa₂Cu₃O₇‑x thin‑film microwave integrated circuits. The review evaluates available substrates for YBCO epitaxy against the specified requirements and highlights current achievements and potential challenges in substrate crystal growth.

Abstract

This review paper presents a discussion on dielectric substrate materials suitable for the preparation of YBa2Cu3O7-x thin-film based microwave integrated circuits. The requirements on the properties of the substrate materials are specified. They cover the properties crucial both for the preparation of high-quality YBa2Cu3O7-x films and for the design of microwave elements. The former includes mainly the lattice match, the match of thermal expansivities, chemical stability, and absence of twinning. The latter includes the relative dielectric permittivity ( epsilon ) and the related tolerances, the microwave loss tangent, and the substrate area required for the accommodation of a microwave circuit. The properties of the currently available substrates suitable for YBCO film epitaxy are discussed in view of these requirements. The main attention is paid to the microwave properties. Current achievements and potential difficulties of the crystal growth technology in the preparation of the substrates are taken into account as well.