A1 Refereed original research article in a scientific journal
The Growth Rate and Temperature Induced Microcracks in YBCO Films Pulsed Laser Deposited on MgO Substrates
Authors: Huhtinen H, Palonen H, Paturi P
Publisher: IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
Publication year: 2013
Journal: IEEE Transactions on Applied Superconductivity
Journal name in source: IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY
Journal acronym: IEEE T APPL SUPERCON
Article number: 7200104
Number in series: 3
Volume: 23
Issue: 3
Number of pages: 4
ISSN: 1051-8223
DOI: https://doi.org/10.1109/TASC.2012.2228891
Abstract
The growth rate and temperature dependence on microcrack formation in YBCO thin films prepared by pulsed laser deposition on MgO (100) substrate is systematically investigated by varying the laser pulse frequency between 1 and 20 Hz and the deposition temperature between 650 degrees C and 850 degrees C. Atomic force microscopy shows that when the growth temperature is high enough, >= 800 degrees C, the higher thermal energy and increased surface mobility during the growth induce a process where adsorbed atoms have more time to find energetically optimal sites, which again result in microcrack formation along the diagonal of a/b-directions in the film. In case of MgO substrate where lattice mismatch in the orthorhombic phase is 8.5% and YBCO grows under tensile strain on it, the growth of YBCO relaxes by rotating the unit cells by 45 degrees in-plane from the substrate (100) and/or (010) directions. The structural defects and reorganization of the material reflect also in the superconducting properties, which are clearly suppressed at high deposition temperatures and with the increasing growth rate. These effects should be taken into account when the pinning structure and superconducting properties of YBCO are optimized for future applications realized on single crystal substrate having small dielectric constant.
The growth rate and temperature dependence on microcrack formation in YBCO thin films prepared by pulsed laser deposition on MgO (100) substrate is systematically investigated by varying the laser pulse frequency between 1 and 20 Hz and the deposition temperature between 650 degrees C and 850 degrees C. Atomic force microscopy shows that when the growth temperature is high enough, >= 800 degrees C, the higher thermal energy and increased surface mobility during the growth induce a process where adsorbed atoms have more time to find energetically optimal sites, which again result in microcrack formation along the diagonal of a/b-directions in the film. In case of MgO substrate where lattice mismatch in the orthorhombic phase is 8.5% and YBCO grows under tensile strain on it, the growth of YBCO relaxes by rotating the unit cells by 45 degrees in-plane from the substrate (100) and/or (010) directions. The structural defects and reorganization of the material reflect also in the superconducting properties, which are clearly suppressed at high deposition temperatures and with the increasing growth rate. These effects should be taken into account when the pinning structure and superconducting properties of YBCO are optimized for future applications realized on single crystal substrate having small dielectric constant.
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