Does N2 gas behave as a surfactant during Ag thin-film sputtering deposition? Insights from in vacuo and real-time measurements - Oxydes en basses dimensions Access content directly
Journal Articles Applied Surface Science Year : 2024

Does N2 gas behave as a surfactant during Ag thin-film sputtering deposition? Insights from in vacuo and real-time measurements

Abstract

Circumventing the thermodynamic trend of 3D growth of noble metals on dielectric substrates to form smooth, continuous ultra-thin films remains a challenge for many applications involving transparent conductive layers such as photovoltaic devices or smart windows. In this context, the use of gaseous species as “surfactants” during the sputtering deposition has attracted much attention in the past few years. The effect of N on the Ag growth on amorphous SiO2 is revisited herein in light of film resistivity and UV-visible differential reflectivity real-time measurements combined with in vacuo x-ray photoemission spectroscopy. Increasing the N content in the Ar gas flow (from 0 to 40%) gives rise to a drastic decrease of the percolation threshold thickness, but at the expense of film conductivity. Photoemission suggests an apparent lack of chemistry between N and Ag, with the absence of N in the bulk and at the surface of the Ag film despite a nitridation of the substrate due to activated species in the plasma. The plasmonic response of Ag nanoparticles evidences the dynamic presence of a N adsorbate that desorbs under vacuum once the growth is stopped. The latter decreases the metal surface energy, thus inducing a flattening of Ag islands before percolation as proved by optics. The adsorption is anisotropic between (111) and (100) facets. All of this explains (i) an earlier percolation resulting from flattened objects and a delayed coalescence, (ii) the change of film texture as seen by ex situ diffraction and (iii) the appearance of unfavourable grain boundaries for electrical transport in continuous films. Considering its immiscibility in the bulk of Ag, its float-out behaviour, its impact on the surface energy and its tendency to desorb at the end of growth, nitrogen has all the characteristics of a “surfactant” for Ag growth.
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Tuesday, July 30, 2024
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Tuesday, July 30, 2024
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hal-04434735 , version 1 (02-02-2024)

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Attribution - NonCommercial - NoDerivatives

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Ramiro Zapata, Matteo Balestrieri, Iryna Gozhyk, Hervé Montigaud, Rémi Lazzari. Does N2 gas behave as a surfactant during Ag thin-film sputtering deposition? Insights from in vacuo and real-time measurements. Applied Surface Science, 2024, 654, pp.159546. ⟨10.1016/j.apsusc.2024.159546⟩. ⟨hal-04434735⟩
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