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The connection between fundamental research and societal applications may play a major role in both directions. In this contribution we present the fabrication and characterization of “solid-gas” nanocomposite films, initially developed for antireflective coatings in solar cells applications. Firstly, it was found that the nanoporous silicon films, obtained by magnetron sputtering (MS) deposition in helium plasma, showed the required reduction of refractive index [1]. The IBA (Ion beam analysis) and TEM-EELS (Transmission Electron Microscopy) techniques showed that the films contained however high amounts of helium trapped inside the nano-pores. The formation of He nano-bubbles was demonstrated [2]. This methodology could also be extended to other matrix elements and to the use of the 3He isotope using a low gas consumption procedure [3]. Helium contents achieved 3.25E18 at/cm2 in a thickness of 1,4 µm for the Si matrix with Helium release starting at 625 K by heating in vacuum [4]. This behavior allowed to propose these films, initially developed for optical applications, as “helium solid targets” for nuclear reaction studies relevant in astrophysics and nuclear structure. These targets avoid the use of cryogenic or high-pressure cells, making them easier to use, reducing energy straggling effects and simplifying the geometry for calculations. Results will be presented from earlier experiments carried out at LNL [3] to recent experiments at TRIUMF-EMMA facilities [5-6].
[1] V. Godinho; J. Caballero-Hernández, D. Jamon; T.C. Rojas, R. Schierholz, J. García-López; F.J. Ferrer; A. Fernández. “A new bottom-up methodology to produce silicon layers with a closed porosity nanostructure and reduced refractive index”. Nanotechnology, DOI: 10.1088/0957-4484/24/27/275604.
[2] B. Lacroix; A. Fernández; N.C. Pyper; A. J.W. Thom; C. T. Whelan. “On the characteristics of helium filled nano-pores in amorphous silicon thin films”. Applied Surface Science, DOI: 10.1016/j.apsusc.2024.161772
[3] A. Fernández; D. Hufschmidt; J. L. Colaux; J. J. Valiente-Dobón; V. Godinho; M.C. Jiménez de Haro; D. Feria; A. Gadea; S. Lucas. “Low gas consumption fabrication of 3He solid targets for nuclear reactions”. Materials & Design, DOI: 10.1016/j.matdes.2019.108337
[4] A. Fernández; M.C. Jiménez de Haro; D. Hufschmidt; O. Montes; T. Sauvage; F.J. Ferrer; A. Caillard; P. Brault; A.-L. Thomann. “Microstructure and composition evolution of He charged solid-gas nanocomposite films of different matrix elements during thermal annealing in vacuum”. Scientific Reports, DOI: 10.1038/s41598-025-06889-8
[5] M. Williams; C. Angus; A. M. Laird; B. Davids; C. Aa. Diget; A. Fernandez; E. J. Williams; A. N. Andreyev; H. Asch; A. A. Avaa et al. “First Measurement of a Weak r -Process Reaction on a Radioactive Nucleus”. Physical Review Letters, DOI: 10.1103/PhysRevLett.134.112701.
[6] https://triumf.ca/2025/03/17/how-do-neutron-star-mergers-and-exploding-stars-create-the-elements/
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