Tailoring of the Distribution of SERS-Active Silver Nanoparticles by Post-Deposition Low-Energy Ion Beam Irradiation

Abstract

The possibility of controlled scalable nanostructuring of surfaces by the formation of the plasmonic nanoparticles is very important for the development of sensors, solar cells, etc. In this work, the formation of the ensembles of silver nanoparticles on silicon and glass substrates by the magnetron deposition technique and the subsequent low-energy Ar+ ion irradiation was studied. The possibility of controlling the sizes, shapes and aerial density of the nanoparticles by the variation of the deposition and irradiation parameters was systematically investigated. Scanning electron microscopy studies of the samples deposited and irradiated in different conditions allowed for analysis of the morphological features of the nanoparticles and the distribution of their sizes and allowed for determination of the optimal parameters for the formation of the plasmonic-active structures. Additionally, the plasmonic properties of the resulting nanoparticles were characterized by means of linear spectroscopy and surface-enhanced Raman spectroscopy. Hereby, in this work, we demonstrate the possibility of the fabrication of silver nanoparticles with a widely varied range of average sizes and aerial density by means of a post-deposition ion irradiation technique to form nanostructured surfaces which can be applied in sensing technologies and surface-enhanced Raman spectroscopy (SERS).

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“…The angle of 40° was set between the ion-beam axis and the normal to the substrate surface. The film thickness and irradiation dose were chosen in accordance with [29], as these deposition parameters ensure low damage to the underlying layer and sufficient SERS effect. The investigated a-C:ND films were synthesized during the second step by means of direct current (DC) magnetron sputtering of the graphite target covered with a 10 µm layer of DND in a pulsed mode (Figures 1 and 2a).…”

“…The angle of 40 • was set between the ion-beam axis and the normal to the substrate surface. The film thickness and irradiation dose were chosen in accordance with [29], as these deposition parameters ensure low damage to the underlying layer and sufficient SERS effect.…”

“…Monocrystallinity ensures the excellent stability of the silver nanoparticles to oxidation and sulfidation [43]. Aside from this, the sufficient thickness of the initial film ensures that the effect of a low-energy ion beam on the subsurface layers of the carbon structure is insignificant [29]. Therefore, the application of the suggested technique to the analysis of a-C:ND all-carbon material has great diagnostic potential.…”

“…However, according to Mie theory, single dipole per particle approximation, and modified long-wavelength approximation, the LSPR position for an individual, spherical, 20 nm particle is ~370-380 nm [45]. As the plasmonic activity of AgNP manufactured by low-energy ion irradiation in similar conditions is considerably larger than for individual nanoparticles [29], the redshift of the observed LSPR wavelength may originate from the hotspot-related interaction between nanoparticles [46,47].…”

“…For the structure analysis, SERS-active nanostructured silver was deposited on the a-C:ND composite by radio-frequency magnetron sputtering of the Ag target, followed by low-energy ion irradiation [28]. The ion-beam treatment method induced the sputtering and surface diffusion of the silver, which lead to the formation of SERS-active nanoparticles [29]. SERS induced by the interaction of a-C:ND and AgNP was applied to analyze the local structural peculiarities of the amorphous carbon matrix and the surface of the composite films formed.…”