ISSN:
1089-7550
Source:
AIP Digital Archive
Topics:
Physics
Notes:
Recently, high-Tc oxide superconductors have been extensively studied because these materials can be applied to various electronic devices, especially highly sensitive magnetic sensors or high-speed switching elements. For such the applications, thin films with superior superconductivity and very smooth surfaces are needed. The purpose of this work is to develop an as-grown technique of Y-Ba-Sr-Cu-O films on comparatively low-temperature substrates by adopting a newly devised alternative sputtering. The sputtering apparatus was constructed by three targets and a substrate holder which was intermittently rotated and stopped facing the desired target. The targets were Y2O, BaO+SrO, and Cu or CuO. The thickness of the oxide layer alternately deposited was adjusted to the thickness of the each metal-oxide monolayer. The substrate used was a (100) plane of a single-crystal MgO. The substrate temperature Ts was changed from 450 to 600 °C. The deposition rate of the each layer was affected by Ts. Especially, the deposition of the CuO layer was very sensitive to conditions of the film growing surface: Ts and/or degree of oxidation. The film composition was adjusted by changing the deposition time of the each layer. The crystal with an oxygen-defective perovskite nucleated even at a Ts of about 500 °C. In the case of sintered bulks, a tetragonal phase was obtained when the content of Sr was comparatively large. In contrast, an orthorhombic phase was stabilized in the sputtered films. As-grown films showed a poor superconductivity. After a post-annealing in 1-atom O2 at a low temperature of about 450 °C, a sharp superconducting transition was observed above 77 K. As we increase the content of Sr, the resistivity of the film became large and semiconductive.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.342202
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