Crystallinity of YBa₂Cu₃O_7−δ Thin Films on Various Buffer Layers for Microwave Devices

Abstract

Buffer layer materials for growing YBa₂Cu₃O_7−δ thin films on MgO substrates are examined from the viewpoint of YBa₂Cu₃O_7−δ thin-film crystallinity. The buffer layers were grown using an excimer laser. Crystallinity of the buffer layers grown on MgO substrates and the YBa₂Cu₃O_7−δ thin films on the buffer layers were evaluated by X-ray diffraction, X-ray rocking curves and X-ray φ-scan methods. One of key points to obtain YBa₂Cu₃O_7−δ thin films of the highest quality on the MgO substrates is the usage of BaZrO₃ buffer layers that are lattice matched to the MgO substrates. However, every buffer layer examined here showed the result of high-quality YBa₂Cu₃O_7−δ thin films with a T_c of around 89 K and low surface resistance.