Non-c-axis-Oriented EuBa_2Cu_3O_<7-δ> Thin Films Grown on Al_2O_3(1102) Substrates with CeO_2 Buffer Layers

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EuBa_2Cu_3O_<7-δ> (EBCO) thin films with different growth orientations were prepared on Al_2O_3(1102) substrates with CeO_2 buffer layers by dc magnetron sputtering. The EBCO thin films were deposited immediately after off-axis rf magnetron sputtering of CeO_2(001) films. The effects of substrate temperature and oxygen concent on epitaxial orientation of EBCO thin films were examined. With the increase in oxygen concentration, the surface roughness of an EBCO thin film increased. An appropriate oxygen concentration existed. It was clarified that the orientation of an EBCO thin film depended on CeO_2 film thickness. The (100)- and (110)-oriented EBCO thin films were obtained on CeO_2 buffer layers 30-90 Å thick and more than 700 Å thick, respectively. The (100)- and (110)-oriented EBCO films had in-plane epitaxial orientation relationships of Al_2O_3[1120] || CeO_2[100] || EBCO [013] and Al_2O_3 [1120] || CeO_2 [100] || EBCO [110], respectively. The (100)-oriented EBCO films deposited on 50-Å-thick CeO_2 (001) buffer layers had T_<ce>'s of 72.0 K, and (110)-oriented EBCO films deposited on 750-Å-thick CeO_2(001) buffer layers had T_<ce>'s of 70.0 K. The T_<ce> decreased with increasing CeO_2 buffer layer thickness above 800 Å. The a-axis-oriented EBCO thin films exhibited T_<ce>'s of about 85.4 K on the 50-Å-thick CeO_2 buffer layers prepared by a self-template method.
社団法人応用物理学会の論文
1999-10-15