Molecular beam epitaxial growth of SmBa2Cu3O7−δ thin films and effect of substrate temperature on the surface roughness |
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Authors: | W. Schindler, P. van Ha elt, J. Markl, P. Bauer, P. Tontsch,G. Saemann-Ischenko |
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Affiliation: | Physikalisches Institut Universität Erlangen-Nürnberg, Erwin-Rommel-Str. 1, 91058, Erlangen, Germany |
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Abstract: | Stoichiometrically optimized, epitaxial SmBa2Cu3O7-δ thin films with high Tc, R = 0 and high critical current densities jc have been prepared for the first time in a tightly controlled molecular beam epitaxy process in non-reactive molecular oxygen, followed by an in situ loading process with molecular oxygen. The surface roughness (on a submicrometre scale) of single-crystal films with their c axes perpendicular to the surface depends markedly on the surface temperature of the substrate during the deposition of the epitaxial films, within a range of only a few degrees centigrade. The calibrated optimal temperature for the preparation of epitaxial films 200 nm thick of this single orientation is found to be 680 ± 5 °C. In scanning tunnelling microscopy investigations, they show a surface roughness of less than 6 nm (five SmBa2Cu3O7−δ unit cells) on a 2 μm × 2 μm scale. At deposition temperatures below this optimal deposition temperature, the well-known a-axis growth increases rapidly, whereas higher temperatures give a significantly higher surface roughness, which can be observed by scanning electron microscopy. |
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