YBa2Cu3O7 − δ thin films with enhanced film properties grown on sapphire using Y2O3/CeO2 bi-layer buffer

Highly epitaxial, microcrack-free thin films of YBa2Cu3O7 − δ (YBCO) have been grown by pulsed laser deposition on sapphire substrates with a double buffer of Y2O3/CeO2. The Y2O3 layer, which has excellent compatibility with CeO2 and YBCO, has been found to be beneficial in reducing the surface porosity of YBCO films as well as inhibiting a-axis-oriented epitaxial growth. The reduction in porosity is attributed to the presence of the Y2O3 layer which acts as a suitable barrier for the chemical reaction occurring at high deposition temperatures between YBCO and CeO2. Due to the improvement in film quality and surface morphology, enhancement of the self-field critical current density (Jc, 77.3 K) by as high as 30% was obtained for a 650-nm thick YBCO film deposited on Y2O3/CeO2 bi-layer buffer compared to simultaneously-deposited YBCO film on CeO2 single-layer buffer only.