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Fabrication and characterization of superconducting nanowires and nanowire networks by electrospinning

Subject Area Experimental Condensed Matter Physics
Term from 2016 to 2020
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 316867631
 
Final Report Year 2021

Final Report Abstract

In summary, the project enabled a fruitful research with the outcome of several publications in respected journals like Phys. Rev. Materials, AIP Advances, Solid State Communications, JMMM and IEEE Transactions on Applied Superconductivity. Several publications more are still in the preparation stage or currently submitted. The PhD student (X. L. Zeng) could successfully complete his thesis, and one master thesis (A. Wiederhold, Micro- and Nanostructures) was finished as well. New research is planned on the YBCO and GdBCO nanowires (see Fig. 7), and for further experiments, an own experimental setup for producing electrospun nanowires will be installed at our institute to enable a more intense work on the nanowire preparation parameters. Furthermore, future research will also consider multiferroic materials where the possibility to spin to different materials together into a hybrid form will be explored in greater detail, following the striking results obtained (see Fig. 6 and [22]). During the project time, we came into contact with several other research groups worldwide showing interest in our nanowire samples. From this, a collaboration with a Brazilian research group (Prof. R. Zadorosny) was established. There, the method of solution-blow spinning is applied [23]. The basic requirements concerning the sol-gel precursors are, however, the same as for electrospinning. So, it is possible to prepare the same material using both techniques and to compare the properties of the outcome. Currently, we are working on nanowires of the RE-123 type to explot the properties of these materials. Originally, we had decided to work with Bi-2212 fearing the dominating GB character of the RE-123 system. The first results, however, show that this is not the case which is promising also in view of possible applications. Another connection was established with a group in Basel (Prof. Poggio) concerning the magnetic measurement of an individual nanowire [24]. The setup for this purpose was not ready for a longer period, and several adjustments had to be made to the system. We sent twice samples for investigation, but not with a real success. Therefore, further investigations and the planned possible knowledge transfer concerning the apparatus itself had to be postponed to 2020, when we hope that the system in Basel will be set up in a way to allow for the planned measurements. A third connection was created at EUCAS 2017 with Prof. E. Zeldov, Weizmann Institute (Israel) which would offer the possibility to employ the most modern SQUID scanning microscope for investigation of our nanowires. A big wish of Prof. Zeldov was to have a sample with electric contacts installed so that the I/V- measurements could be performed at the same time as the scanning SQUID data, therefore, these experiments will be carried out after a successful repetition of the electric single nanowire measurements with the contacts prepared at KIT, Karlsruhe. The connections built up within an INTERREG IVa project (GRMN) were used to perform several runs of magneto-optic imaging in Liège on the various nanowire network samples, as well as magnetic measurements by SQUID magnetometry in Nancy. Results of this collaboration are currently in preparation for publication. Via our relation to Dr. Mark Rikel, who is now working at D-NANO and is an expert of the chemical side of the fabrication of Bi-2212 and Bi-2223 wires, we came in contact with the activities of D-NANO. This company is working in a side direction on ink-jet printing of YBCO powders with the idea to prepare superconducting interconnects without extra need of structuring steps. We started to a collaboration with them to employ our nanowires for the ink-jet printing [6]. From their experience, we learned the required size limits of the particles. Finally, we started to apply for measurement time and help at the user facility of KIT, Karlsruhe to improve our way of creating electric contacts to individual nanowires. This step proved to be an essential issue for the I/V and resistance measurements of the nanowire samples, as it was now possible to obtain electric contacts to the nanowires with a reasonable contact resistance to enable proper electric measurements. In summary, during the project time we could establish many fruitful collaborations with researchers in Germany, in the Greater Region (Lothringen, Wallonie, Saarland, Rhineland- Palatinate) and worldwide (Brazil, Israel, Switzerland). Several research on the nanowires will be ongoing in the next years, where we already have established the respective contacts. The idea of having applications of superconducting and / or ferromagnetic nanowires will certainly bring out new solutions and possibilities, as we have just explored the top of the iceberg. And we will certainly apply in the future for new projects with well-defined directions towards applications and/or towards basic research topics.

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