Surface Morphology of Cerium Oxide Layer and its Effect on the Performance of Superconducting Layer

Abstract

So far, huge progress has been achieved in coated superconductor wires with high performance, where cerium oxides (CeO2) usually figure as superior buffer layer. However, the influence of CeO2 layer’s surface morphology on the performance of YBCO layer is still illusive. In this work, we fabricated CeO2 layers with similar texture and diverse surface characteristics by altering process parameters on IBAD-MgO substrate and then deposited YBCO layers on these CeO2 layers by a reel-to-reel pulsed laser deposition (PLD) system. The abnormal relationship between the quality of YBCO layer and the surface morphology of CeO2 layer was investigated. Instead of texture quality, the critical current density of YBCO-coated layer is highly susceptible to the surface morphology of CeO2 layer, once their surface roughness root mean square (RMS) outstrips the threshold of atomic flat. And our study indicates RMS and flat area fraction are all key issues for PLD epitaxial multilayers but play in different priority. The possible defect formation process of YBCO/CeO2 was also discussed on the basis of the SEM images.