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Conducting nanowires in insulating ceramics

Abstract

Low-dimensional structures, such as microclusters, quantum dots and one- or two-dimensional (1D or 2D) quantum wires, are of scientific and technological interest due to their unusual physical properties, which are quite different from those in the bulk1,2,3,4. Here we present a successful method for fabricating conducting nanowire bundles inside an insulating ceramic single crystal by using unidirectional dislocations. A high density of dislocations (109 cm−2) was introduced by activating a primary slip system in sapphire (α-Al2O3 single crystal) using a two-stage deformation technique. Plate specimens cut out from the deformed sapphire were then annealed to straighten the dislocations. Finally, the plates on which metallic Ti was evaporated were heat-treated to diffuse Ti atoms inside sapphire. As a result of this process, Ti atoms segregated along the unidirectional dislocations within about 5 nm diameter, forming unidirectional Ti-enriched nanowires, which exhibit excellent electrical conductivity. This simple technique could potentially to be applied to any crystal, and may give special properties to commonly used materials.

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Figure 1: The fabrication process of a 1D nanostructure bundle.
Figure 2: Transmission electron microscope bright-field images showing the dislocation structures formed by the two-stage deformation technique and the post-annealing process.
Figure 3: Composition and chemical bonding around the unidirectional dislocations after the Ti infiltration process.
Figure 4: Typical current-mapping images obtained from the sapphire plate by using the contact-current mode of the scanning probe microscope.

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Acknowledgements

The authors acknowledge K. P. D. Lagerlöf for useful discussions. This work was supported by PRESTO, Japan Science and Technology Corporation, and the Active Nano-characterization and Technology project, MEXT, Japan.

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Correspondence to Yuichi Ikuhara.

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Nakamura, A., Matsunaga, K., Tohma, J. et al. Conducting nanowires in insulating ceramics. Nature Mater 2, 453–456 (2003). https://doi.org/10.1038/nmat920

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