Electromagnetic Characterization of YBa2Cu3O 7-δ Thin Films With Calcium Doping for Bi-Crystal Grain Boundary Conductivity Enhancement

Document Type

Article

Publication Date

3-1-2008

Abstract

The objective of this study was to examine the transport properties of two YBa2Cu3O7−δ thin films with (Y0.9Ca0.1)2BaCuO5 additions deposited on vicinal SrTiO3 6° bi-crystal substrates and to investigate the possible correlations between spatial calcium distribution and local electromagnetic properties across bi-crystal grain boundaries using evanescent microwave microscopy (EMM) and atomic force microscopy (AFM). The samples under consideration differed in transport critical current measurements by a factor of two although they were deposited on the same type of bi-crystal substrate. A near-field evanescent microwave microscope based on a coaxial transmission line resonator with an end-wall aperture was used to measure changes in conductivity local to the bi-crystal boundary of YBa2Cu3O7−δ thin films below (79.2 K) and above (room temperature) the superconducting transition temperature. Atomic concentration measurements by electron microprobe analysis were performed in the same regions, and a clear correlation between calcium distribution and conductivity at 79.2 K (as represented by the change in quality factor) was found. Surface potential imaging (SPI) and quality factor scans in the area of the bi-crystal grain boundaries were performed at room temperature using AFM and EMM, respectively, to evaluate local electromagnetic properties in the normal state and investigate their correlation with superconducting properties.

DOI

10.1088/0953-2048/21/3/035008

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