Influence of Crystal Strain on Superconductivity of a-Axis Oriented YBa 2 Cu 3 O x Films

• Published in: Japanese Journal of Applied Physics Vol. 33; no. 10R; p. 5701
• Main Authors: Ito, Wataru, Mahajan, Sukesh, Yoshida, Yukihisa, Morishita, Tadataka, Kumagai, Masao, Yabuta, Konami
• Format: Journal Article
• Language: English
• Published: 01-10-1994
• ISSN: 0021-4922; 1347-4065
• DOI: 10.1143/JJAP.33.5701

Ion channeling measurements were executed to evaluate the crystal strain in
a
-axis
oriented YBa
2
Cu
3
O
x
(YBCO) films with different film thicknesses.
The average Ba-Ba distance in the film plane as determined from the channeling angle
of the Ba atomic row in the (and ) direction
was found to be close to the lattice constant of the SrTiO
3
substrate regardless
of the film thickness. A similar result was also obtained for oxygen atoms. These results
indicate that the films grow while matching their lattice constant to that of the substrate.
The simultaneous strain relief induced by the increase in film thickness was suggested
from the channeling yield in the obtained dip curve. Furthermore, the relaxed grain was
confirmed near the surface of the 3500 Å film from the Ba axial
channeling. The influence of the crystal strain on the superconductivity of the
a
-axis oriented YBCO films is explained on the basis of variation in the site of apical oxygen.