Xiaochu Yang

Date of Award

6-11-2002

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

First Advisor

Tar-Pin Chen

Abstract

The purpose of the work reported in this dissertation is to find buffer layer materials for YBa2 C u3 0 7 (YBCO) superconducting multilayers and electronic devices. The buffer layer should have lattice parameters a, b, and c close to the lattice parameters o f YBa2Cu3 0 7 so that the superconducting property o f YBCO will not be altered. It is desirable that the fabrication conditions o f the buffer layer materials be the same as that for YBCO so that the fabrication process can be simplified. Finally the buffer layers which separate the YBCO films in the multilayers or devices should provide adequate insulation to YBCO layers. PrBa2 Cu3 0 7 (PBCO) satisfies the first two requirements but comes out short for the last one. To improve this we substituted Cu in PBCO by 5%, 10%, 15% and 20% o f Ni, Fe, or Al and performed x-ray and resistivity measurements on PBCO and the substituted samples. The x-ray data indicated that the lattice parameters of the substituted PBCO are very close to those o f PBCO. The fabrication conditions o f the substituted PBCO are the same as those for PBCO. Resistivity for most o f the substituted samples, on the other hand, is orders o f magnitude higher than that o f PBCO. These results suggest that the Ni, Fe and Al substituted PBCO are better buffer materials than PBCO for YBCO multilayers and electronic devices.

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