Growth of Complex Epitaxial Multi-Component Oxide Thin Films and Heterostructures with Strong Anisotropy
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Growth of Complex Epitaxial Multi-Component Oxide Thin Films and Heterostructures with Strong Anisotropy Kazuhiro Endo1, Petre Badica2, Hidehito Nanto1, Yoshinori Takei1, Shunichi Arisawa3, Hirofumi Yamasaki4, Katherine Develos-Bagarinao4, Tamio Endo5 1
Kanazawa Institute of Technology, 3-1 Yatsukaho, Hakusan, Ishikawa 924-0838, Japan National Institute of Materials Physics, Atomistilor 105bis, Bucharest-Magurele 077125, Romania 3 National Institute for Material Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan 4 National Institute of Advanced Industrial Science and Technology, 1-1-1 Umezono Tsukuba, Ibaraki 305-8568 Japan 5 Mie University, 1577 Kurima, Tsu, Mie 514-8507, Japan 2
ABSTRACT We briefly review our data on MOCVD growth problems of sandwich stacked heterostructures based on Bi-Sr-Ca-Cu-O and YBa2Cu3O7 high temperature superconductors. Non-superconducting layers were (Ca, Sr)CuO2, (Ca, Ba)CuO2 and Bi4Ti3O12. Structures were with c-axis normal or inclined with about 45 vs. the surface of the substrate. Film-substrate lattice relationship, growth mechanism and the resulting morphology controlling roughness and uniformity, stability domain of the phases and inter diffusion are all important aspects toward significant progress in the field. Our analysis indicates that requirements are more severe for non-c-axis heterostructures, and suggest some ideas for further improvements.
INTRODUCTION Heterostructures can be built as stacks of alternate two-dimensional layers. The most common approach is to stack materials with layered structures having c-axis parallel to each other and normal to the substrate. For a superconductor- non-superconductor- superconductor heterostructure this is the most convenient geometry to generate a tunnelling-junction device. However, low coherence length of HTS along c-axis translates into necessity to produce a very thin non-superconducting layer with thickness comparable with coherence length (2 nm). Technically this is challenging and a non-c axis heterostructure can be the solution. For the non c-axis heterostructures, layers may have different orientations between them and with the substrate so that it would be possible to take advantage of the anisotropy features of the HTS-layer and of the longer coherence length on directions other than along c-axis. It is expected that non-c axis heterostructures can provide new possibilities for fabrication of devices and for their functionality. In this work we briefly review our results on the MOCVD growth aspects of c-axis and non-c axis heterostructures based on Bi-Sr-Ca-Cu-O and YBa2Cu3O7 high temperature superconductors (HTS) looking for new solutions.
EXPERIMENTAL DETAILS Thin films and heterostructures of c-axis and non-c axis orientations were grown by MOCVD [1-7]. Heterostructures of c-axis type were: A1=(100)STO/(001)Bi2223/(001)BTO, A2=(100)STO/(001)BTO/(001)Bi-2212, B1=(100)STO/(001)Bi2223/(001)SCCO, B2=(100)STO/(001)SCCO/(001)Bi2212, B3=(100)STO/(001)Bi2223/(001)SCCO/(001)Bi2212, C1=(100)STO/(001)Bi2223/(001)BCCO, C2
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