Crystallinity of YBa2Cu3O7-.DELTA. Thin Films on Various Buffer Layers for Microwave Devices

Buffer layer materials for growing YBa2Cu3O7−δ thin films on MgO substrates are examined from the viewpoint of YBa2Cu3O7−δ thin-film crystallinity. The buffer layers were grown using an excimer laser. Crystallinity of the buffer layers grown on MgO substrates and the YBa2Cu3O7−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 YBa2Cu3O7−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 YBa2Cu3O7−δ thin films with a Tc of around 89 K and low surface resistance.