Non-c-axis-Oriented EuBa2Cu3O7-δ Thin Films Grown on Al2O3(11̄02) Substrates with CeO2 Buffer Layers

Abstract

EuBa2Cu3O7-δ (EBCO) thin films with different growth orientations were prepared on Al2O3(11̄02) substrates with CeO2 buffer layers by dc magnetron sputtering. The EBCO thin films were deposited immediately after off-axis rf magnetron sputtering of CeO2(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 CeO2 film thickness. The (100)- and (110)-oriented EBCO thin films were obtained on CeO2 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 Al2O3[11̄20] ∥CeO2[100] ∥EBCO[013] and Al2O3[112̄0] ∥CeO2[100] ∥EBCO[11̄0], respectively. The (100)-oriented EBCO films deposited on 50-Å-thick CeO2 (001) buffer layers had Tce's of 72.0 K, and (110)-oriented EBCO films deposited on 750-Å-thick CeO2(001) buffer layers had Tce's of 70.0 K. The Tce decreased with increasing CeO2 buffer layer thickness above 800 Å. The a-axis-oriented EBCO thin films exhibited Tce's of about 85.4 K on the 50-Å-thick CeO2 buffer layers prepared by a self-template method.