Quasi-one-dimensional metallic conduction channels in exotic ferroelectric topological defects

Topological objects and defects (e.g. skyrmions, domain walls, vortices,) in condensed matters have attracted a lot of interest as a field for exploring emerging exotic phenomena and functionalities.*

In materials with ferroic order, these topological objects can also be manipulated and controlled by external fields without disrupting their host lattice, making them promising elemental building blocks for potential configurable topological nanoelectronics. *

Ferroelectric topological objects provide a promising area for investigating emerging physical properties that could potentially be utilized in future nanoelectronic devices. *

In the article “Quasi-one-dimensional metallic conduction channels in exotic ferroelectric topological defects” Wenda Yang, Guo Tian, Yang Zhang, Fei Xue, Dongfeng Zheng, Luyong Zhang, Yadong Wang, Chao Chen, Zhen Fan, Zhipeng Hou, Deyang Chen, Jinwei Gao, Min Zeng, Minghui Qin, Long-Qing Chen, Xingsen Gao and Jun-Ming Liu demonstrate the existence of metallic conduction superfine (<3 nm) channels in two types of exotic topological defects, namely a quadrant vortex core or simply vortex core and a quadrant center domain core or simply center core, in an array of BiFeO3 (BFO) nanoislands.*

The authors discover via the phase-field simulation that the superfine metallic conduction channels along the center cores arise from the screening charge carriers confined at the core region, whereas the high conductance of vortex cores results from a field-induced twisted state. These conducting channels can be reversibly created and deleted by manipulating the two topological states via electric field, leading to an apparent electroresistance effect with an on/off ratio higher than 103.*

The findings by Wenda Yang et al. open up the possibility of using these functional one-dimensional topological objects in high-density nanoelectronic devices, e.g. nonvolatile memory.*

NanoWorld PlatinumIdridium5 coated Arrow-EFM AFM probes were used to examine the domain structures by vector piezoresponse force microscopy (PFM). By using vector PFM mode, the authors could simultaneously map the vertical and lateral piezoresponse signals from the nanoisland one by one.*

NanoWorld Conductive Diamond coated AFM probes CDT-NCHR were used for the conductive current distribution maps, current–voltage (I–V) measurements that were characterized by conductive atomic force microscopy (C-AFM).

Fig. 2 from “Quasi-one-dimensional metallic conduction channels in exotic ferroelectric topological defects” by Wenda Yang et al.:
The domain structures and corresponding conductive properties for both a vortex and a center topological states confined in two nanoislands.
a, b PFM and C-AFM images for both a vortex state (a) and a center state (b), the micrographs from the left to the right are PFM vertical phase images illustrating the uniform upward vertical polarization components for both nanoislands, the PFM lateral phase images recorded at sample rotation of 0o and 90o to evaluate the directions of lateral polarization components respectively along x axis ([100] axis) and y axis ([100] axis), the lateral polarization vector direction maps derived from the PFM data, and corresponding C-AFM maps. The thick arrows aside the PFM images mark the directions of the cantilever for each PFM scan, and the fine arrows inside the images mark the directions of polarization components perpendicular to the directions of the cantilever. c, d Extracted current spatial profiles from the C-AFM maps for both the vortex (c) and the center (d) cores, extracted from a and b, respectively. The inserts in c and d illustrate the C-AFM maps and schematic local polarization configurations for the two topological cores. e Temperature-dependent conductive current (I–V) curves for both topological cores and domain walls.*

*Wenda Yang, Guo Tian, Yang Zhang, Fei Xue, Dongfeng Zheng, Luyong Zhang, Yadong Wang, Chao Chen, Zhen Fan, Zhipeng Hou, Deyang Chen, Jinwei Gao, Min Zeng, Minghui Qin, Long-Qing Chen, Xingsen Gao and Jun-Ming Liu
Quasi-one-dimensional metallic conduction channels in exotic ferroelectric topological defects
Nature Communications volume 12, Article number: 1306 (2021)
DOI: https://doi.org/10.1038/s41467-021-21521-9

Please follow this external link to read the full article: https://rdcu.be/cg0JY

Open Access : The article “Quasi-one-dimensional metallic conduction channels in exotic ferroelectric topological defects” by Wenda Yang, Guo Tian, Yang Zhang, Fei Xue, Dongfeng Zheng, Luyong Zhang, Yadong Wang, Chao Chen, Zhen Fan, Zhipeng Hou, Deyang Chen, Jinwei Gao, Min Zeng, Minghui Qin, Long-Qing Chen, Xingsen Gao and Jun-Ming Liu is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/.

Flexible 3D Electrodes of Free-Standing TiN Nanotube Arrays Grown by Atomic Layer Deposition with a Ti Interlayer as an Adhesion Promoter

Nanostructured electrodes and their flexible integrated systems have great potential for many applications, including electrochemical energy storage, electrocatalysis and solid-state memory devices, given their ability to improve faradaic reaction sites by large surface area. Although many processing techniques have been employed to fabricate nanostructured electrodes on to flexible substrates, these present limitations in terms of achieving flexible electrodes with high mechanical stability.*

In the study “Flexible 3D Electrodes of Free-Standing TiN Nanotube Arrays Grown by Atomic Layer Deposition with a Ti Interlayer as an Adhesion Promoter” by Seokjung Yun, Sang-Joon Kim, Jaesung Youn, Hoon Kim, Jeongjae Ryu, Changdeuck Bae, Kwangsoo No and Seungbum Hong, the adhesion, mechanical properties and flexibility of TiN nanotube arrays on a Pt substrate were improved using a Ti interlayer. Highly ordered and well aligned TiN nanotube arrays were fabricated on a Pt substrate using a template-assisted method with an anodic aluminum oxide (AAO) template and atomic layer deposition (ALD) system.*

The authors show that with the use of a Ti interlayer between the TiN nanotube arrays and Pt substrate, the TiN nanotube arrays could perfectly attach to the Pt substrate without delamination and faceted phenomena. Furthermore, the I-V curve measurements confirmed that the electric contact between the TiN nanotube arrays and substrate for use as an electrode was excellent, and its flexibility was also good for use in flexible electronic devices. Future efforts will be directed toward the fabrication of embedded electrodes in flexible plastic substrates by employing the concepts demonstrated in this study.*

The presented strategy provides a new class of nanostructured 3D electrodes to overcome critical mechanical stability, thus providing a great potential platform for application in a flexible integrated device.*

Topography and transport properties were investigated using a conductive atomic force microscope with NanoWorld Pointprobe® EFM AFM probes ( Pt-coated conductive AFM tips).*

Figure 5 from “Flexible 3D Electrodes of Free-Standing TiN Nanotube Arrays Grown by Atomic Layer Deposition with a Ti Interlayer as an Adhesion Promoter” by Seokjung Yun et al.:
Analysis of TiN NTs/ Ti / Pt samples (a) XRD, (b) schematic of C-AFM setup, (c) AFM height image, and (d) local I-V curve by C-AFM.

*Seokjung Yun, Sang-Joon Kim, Jaesung Youn, Hoon Kim, Jeongjae Ryu, Changdeuck Bae, Kwangsoo No and Seungbum Hong
Flexible 3D Electrodes of Free-Standing TiN Nanotube Arrays Grown by Atomic Layer Deposition with a Ti Interlayer as an Adhesion Promoter
Nanomaterials 2020, 10, 409
DOI: 10.3390/nano10030409

Please follow this external link for access to the full article: https://doi.org/10.3390/nano10030409

Open Access The article “Flexible 3D Electrodes of Free-Standing TiN Nanotube Arrays Grown by Atomic Layer Deposition with a Ti Interlayer as an Adhesion Promoter“ by Seokjung Yun, Sang-Joon Kim, Jaesung Youn, Hoon Kim, Jeongjae Ryu, Changdeuck Bae, Kwangsoo No and Seungbum Hong is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.