The applied research efforts targeting smaller device sizes at constant or improved performance frequently faces issues related to material quality [1]. Advanced fabrication techniques have demonstrated that compositions and dimensions can be controlled to a significant extent in thin film, multilayers [2], or patterned elements thereof. In these cases, the vertical scales are usually comparable or (much) smaller than the horizontal ones. On the other hand, it can be very challenging to maintain the same level of control while going into the third dimension.
Taking nanowires i.e. elongated rods with sub-micron diameters as an example, one could argue that top-down approaches via chemical etching enable precise shape control combined with material quality [3,4]. Distinct fabrication techniques such as molecular beam epitaxy [5,6], Focused Electron/Ion Beam-Induced Deposition [7,8,9] or electrochemical filling of templates [10,11] provide additional valuable strategies. However, none of the above can offer simultaneously (i) fine control over the geometry, (ii) excellent composition control, (iii) lateral protection against oxidation, (iv) and the prospect of single-crystalline growth. In this presentation, I would like to describe a physical and template-based nanowire fabrication scheme which should, in many instances, provide these four characteristics. The general idea consists in reaching a high-temperature plasticity regime that is dominated by matter diffusion [12,13,14]. This phenomenon allows nanowire growth even in pores a few tens of nanometers in diameter, as available in porous alumina membranes. First of all, I am going to provide an overview of literature reports on nanowires obtained with this method, and discuss the mechanisms at play (along with their limitations). I will then describe my research project at Institut Néel, which shall require a strong focus on high-pressure, high-temperature nanowire extrusion. The long-term goal, namely magnetic field microscopy, involves the use of such objects as tailored magnetic force sensors.

1. Bharat Bhushan (ed.), Springer Handbook of Nanotechnology, 4th edition (2017). DOI: 10.1007/978-3-662-54357-3
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12. Z. Liu, Nat. Comm., vol. 8, p.14910, 2016. DOI: 10.1038/ncomms14910
13. Z. Liu, Phys. Rev. Lett., vol. 122(016101) 2019. DOI: 10.1103/PhysRevLett.122.016101
14. N. Liu et al., Sci. Adv., vol. 7, 2021. DOI: 10.1126/sciadv.abi4567

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More information :https://www.spintec.fr/seminar-high-pressure-high-temperature-extrusion-of-nanowire-resonators-for-magnetic-field-microscopy/​​

Videoconference ​: https://univ-grenoble-alpes-fr.zoom.us/j/98769867024?pwd=dXNnT3RMeThjYStybGVQSUN0TVdJdz09