Evolution of morphology, crystallinity, and growth modes of thin superconducting YBa2Cu3O7−x films on SrTiO3 and NdGaO3 substrates

Publisher Website
Google Scholar
Abstract
The evolution of surface morphology, crystallinity, and growth modes of c‐axis‐oriented superconducting YBa2Cu3O7−x (YBCO)thin filmsdeposited by pulsed laser deposition on SrTiO3(100) and NdGaO3(110) substrates have been systematically investigated with scanning electron microscopy(SEM),atomic force microscopy(AFM),transmission electron microscopy(TEM), x‐ray energy‐dispersive spectroscopy, and x‐ray diffraction. SEM and AFM images of the YBCOfilmsgrown on NdGaO3 with a sequential thickness revealed that the films were rather smooth and grew in a two‐dimensional manner. In contrast, the YBCOfilms of the same thickness on SrTiO3 were found to have spiral growth features, even in the thinnest film (10 nm or 8 unit cells thick) indicating that an island growth mechanism took place. A change of the full width at half‐maximum of the rocking curves of the (005) reflection with the film thickness showed that the crystallinity of the films on NdGaO3 was much better than those grown on SrTiO3, suggesting that a lattice match is a crucial factor to obtain good crystallinity. In the early stages of growth the preferential a‐axis orientation of the films on NdGaO3, as revealed by TEM, was consistent with the smooth and featureless film surfaces found, in contrast to the c‐axis growth mode on SrTiO3.