Growth of Laser Ablated YBa2Cu3O7 Thin Films Epitaxied on (100)MgO: Influence of In-Plane Misorientations on Low and High Frequency Properties |
| A. Perrin, M. Guilloux-Viry and X. Castel Laboratoire de Chimie du Solide et Inorganique Moléculaire, URA CNRS 1495, Université de Rennes I, Avenue du Général Leclerc, 35042 Rennes-Cedex, France |
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| The graphoepitaxial growth of c-axis YBa2Cu3O7 laser ablated thin films on (100)MgO induces a competition between two main in-plane orientations due to the large lattice mismatch: ⟨100⟩ YBa2Cu3O7 ∥ ⟨100⟩ MgO, c⊥ 0 notation or ⟨110⟩ YBa2Cu3O7 ∥ ⟨100⟩ MgO, c⊥ 45 notation. The ratio of c⊥ 45/c⊥ 0 in-plane orientations (η), measured by X-ray diffraction φ scans, is ranging from 0.2% to 49.7% for the films reported here. Their crystalline qualities were compared on the basis of rocking curves (Δθ), electron channeling patterns and reflection high energy electron diffraction diagrams. The coexistence of c⊥ 0 and c⊥ 45 domains creates high angle grain boundaries. No degradation of Tc, residual resistance ratio (RRR) or ΔTc is observed when η increases. In contrast, a strong correlation between microwave losses characterized by surface resistance (RS at 10 GHz and 77 K), inductive losses S(χ") (surface of the χ" peak obtained in a.c. susceptibility at 119 Hz) and η was clearly evidenced. A minimum of losses was found for η between 3 and 6% suggesting the necessity of a low quantity of high angle grain boundaries for films optimization. Finally, some specific processes carried out recently in order to try to efficiently control η, then RS are discussed. |
| DOI: 10.12693/APhysPolA.92.115 PACS numbers: 68.55.Jk, 81.15.-z, 73.25.+i |