Crystalline Orientation Control in Bi-Sr-Ca-Cu-O Thin Films
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CRYSTALLINE ORIENTATION CONTROL IN Bi-Sr-Ca-Cu-0 THIN FILMS
Yoshiki Ishizuka, Yoshiaki Terashima and Tadao Miura Toshiba Research and Development Center, 1 Komukai Toshiba-cho, Saiwai-ku, Kawasaki 210, Japan
ABSTRACT Bi-Sr-Ca-Cu-0
thin
films
were
prepared
on
(110)SrTiO 3
by
coevaporation with rf oxygen plasma. The non-(00n) crystalline orientations were formed in the Bi 2 Sr 2 Ca2Cu30 yI Bi 2Sr 2 CaCu 2 0 2,9 and Bi 2 Sr 2 CuOy 3
phases.
Furthermore,
it
was
confirmed
that
the
chemical
composition and the oxygen plasma condition influenced the crystalline orientation. On the basis of these results, a new idea for the film growth mechanism is proposed. INTRODUCTION The crystalline orientation in Bi-Sr-Ca-Cu-0 thin films deposited on (100)SrTiO 3 or (100)MgO substrates was only (00n) orientation[l,2]. This orientation has been considered to be caused by the structural two-dimensionality of this compound. On the other hand, the two-dimensionality influences the superconducting properties. For example, the coherence length perpendicular to the c-axis is much greater than that measured parallel to the c-axis. Thus, the formation of those orientations other than (00n) orientation is a great importance, both for understanding the film growth mechanism and for fabricating multilayer structures, such as Josephson junctions[3,4]. In this paper, the formation of non-(0On) orientations[5-8] is reported. Furthermore, the effects of chemical composition and the oxygen plasma condition on the crystalline orientation[5] between non-(00n) orientations and (00n) orientation are also discussed. On the basis of these results, the authors propose a new idea for the film growth mechanism of Bi-Sr-Ca-Cu-O. EXPERIMENTAL The thin films of Bi-Sr-Ca-Cu-O were deposited by coevaporation using an MBE machine[9]. Bi, Sr, Ca, and Cu were evaporated from individual Knudsen-cells (K-cell), and individual evaporation rates were measured with a quartz crystal thickness monitor. Oxygen plasma, excited by radio-frequency (rf: 13.56 MHz), was used as an effective oxidizing source. All the metal elements and an oxygen plasma generated in a quartz tube were supplied simultaneously to a (110)SrTiO3 substrate. The substrate temperature was kept constant at about 800 °C during the 90-minute deposition. Oxygen plasma was continued after the deposition until the substrate temperature cooled down to room temperature. The authors investigated the effects of chemical composition and the oxygen plasma condition on the crystalline orientation. The chemical composition effect was examined by varying the Sr composition. On the other hand, the oxygen plasma condition was varied by regulating the oxygen flow rate into the chamber or by regulating the rf power. The Mat. Res. Soc. Symp. Proc. Vol. 223. ©1991 Materials Research Society
Downloaded from https://www.cambridge.org/core. University of Texas Libraries, on 29 May 2020 at 23:34:42, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10
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