Morphology evolvement of CeO2 cap layer for coated conductors

► We investigated the morphology of CeO2 cap layers influence by substrate temperature and deposition rate. ► AFM exhibited the grain shape grown from granule to cluster with the temperature increasing, the grain size decreased as the sputter power increased, and their mechanisms were proposed. ► The root mean square surface roughness of the best sample was 1.8 nm over a 3 μm × 3 μm area. ► The YBCO layer with thickness of 1.36 μm exhibited a Jc of 1.72 MA/cm2 at 77 K.