Tailored High-Tc Superconducting Thin Films Prepared by Layer-By-Layer Deposition with Excimer Laser
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TAILORED HIGH-Tc SUPERCONDUCTING THIN FILMS PREPARED LAYER-BY-LAYER DEPOSITION WITH EXCIMER LASER
BY
Tomoji KAWAI, Masaki KANAI, Hitoshi TABATA and Shichio KAWAI and Industrial Research, The Institute of Scientific Osaka University, Mihogaoka, Ibaraki, Osaka 567 Japan
ABSTRACT deposition method with By using layer-by-layer successive CuO 2 planes in the excimer laser ablation, the distance between and has been controlled Bi 2 Sr 2 Ca.Cu 2 Oy superconductor superlattices with concentration modulation of Y and Ca have been films', it is From the properties of these 'Tailored formed. between CuO 2 layers across suggested that there is an interaction very weak the Tc value, but there is a Ca layer to affect across Bi 2 0 2 blocking layers. interaction I.
INTRODUCTION
CuO 2 structural feature of high-Tc cuprates is The essential The CuO 2 layers are separated layers doped with charge carriers. to form the two blocking layers and mediating layers by Here, the blocking layers include dimensional layered structure. Bi 2 0 2 , T1 2 0 2 , fluorite(Nd 2 02 layers of rock salt (LaO, SrO etc.), small PbO and Cu 9chains• and mediating layers include far and Y . Any of the superconductors so cations, such as Ca discovered can be classified by the combination of these blocking layers and mediating layers. control In order to control the superconductivity, we should layers, the unit of CuO 2 -based structure sandwiched by blocking the number of CuO 2 layers, spacing between CuO 2 layers that is, layers are and Cu-O bond length. When the numbers of the CuQ 2 of incorporation fixed, these structures can be changed by the above and/or with different ionic radii between, exotic ions 'Tailored these below the CuO 2 layers. (Fig. 1) The formation of carlilf out by using layer-by-layer thin films' have been successive deposition method. to the this layer-by-layer method can also be applied Since unit cells, we the different control of the composition across and are able to form superlattices by modulating concentration with across each unit cell layer in combination composition various blocking layers and mediating layers. the recently developed 'layer-by-layer We report here laser ablation' for the successive deposition method using structure and also for the formation of control of the superlattices in the 'Tailored Superconducting Films.' the distance between CuO 2 The results presented here are, (1) into the layers is changed by inserting bigger ions, such as Ba, (BSCCO), and (1j) layers of Bi 2 Sr 2 Ca 1 CU2 0 8 structure Ca Y superlittice formation with the concentration modulation of From and Ca + based on the Bi 2 Sr 2 (Cal-xYx)CU20 8 superconductor. across blocking we argue that the interaction these experiments, is strong layers is very weak and that across mediating layers and important to determine the Tc value.
"etc.),
Mat. Res. Soc. Symp. Proc. Vol. 169. ©1990 Materials Research Society
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II.
EXPERIMENTAL
The a~pgfatus used for the film formation has been already reported. ''I The emitted atoms and molecules by
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