Microstructures and enhancement of critical current density in YBa/sub 2/Cu/sub 3/O/sub 7/ thin films grown by pulsed laser deposition on various single crystal substrates modified by Ag nano-dots

A. H. Li, University of Wollongong
M. Ionescu, University of Wollongong
H. K. Liu, University of Wollongong
T. Silver, University of Wollongong
X. L. Wang, University of Wollongong
S. X. Dou, University of Wollongong

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This paper originally appeared as: Li, AH, Ionescu, M, Liu, HK et al, Microstructures and enhancement of critical current density in YBa/sub 2/Cu/sub 3/O/sub 7/ thin films grown by pulsed laser deposition on various single crystal substrates modified by Ag nano-dots, IEEE Transactions on Applied Superconductivity, June 2005, 15(2)3, 3046-3049. Copyright IEEE 2005.

Abstract

YBa/sub 2/Cu/sub 3/O/sub 7/ (Y123) thin films were grown by pulsed laser deposition (PLD) on YSZ (100), SrTiO3 (100), and LaAlO3 (100) single crystal substrates. Prior to the film deposition, a discontinuous layer of Ag nano-dots was deposited on the substrates. The Y123 films grown on such surfaces modified with Ag nano-dots were characterized by Atomic Force Microscopy (AFM), X-ray diffraction (XRD), scanning electron microscopy (SEM), AC susceptibility and DC magnetization. The effects of the density of Ag nano-dots, which was controlled by the numbers of PLD shots, on the microstructures and resultant critical current density J/sub c/ have been studied systematically. Results showed that at fixed physical deposition conditions J/sub c/ increased monotonically with number of Ag shots, n, for films grown on both STO and LAO substrates. At 77 K, the J/sub c/ increased from 10/sup 6/ to 3.2/spl times/10/sup 6/ A/cm/sup 2/ for LAO and from 8/spl times/10/sup 5/ to 3.5/spl times/106 A/cm/sup 2/ for STO as n increased from 0 to 150. At 5 K, the enhancement of J/sub c/ was approximately four times at both low and high fields. However, for films grown on YSZ substrate, J/sub c/ increased from 2/spl times/10/sup 5/ to 2/spl times/10/sup 6/ A/cm/sup 2/ as Ag shots increased from 0 to 30, and decreased to 9/spl times/10/sup 5/ for n/spl ges/60. Detailed microstructure investigations indicated that the crystallinity and ab alignment gradually improved as the number of Ag-nano-dots increased.