Shape elongation of Zn nanoparticles in silica irradiated with swift heavy ions of different species and energies: scaling law and some insights on the elongation mechanism

Abstract

Zinc nanoparticles (NPs) embedded in silica were irradiated with swift heavy ions (SHIs) of seven different combinations of species and energies. The shape elongation induced by the irradiations was evaluated by optical linear dichroism (OLD) spectroscopy, which is a sensitive tool for determining the change in the mean aspect ratio (AR) of NPs. Although the mean AR change indicated a linear fluence dependence in the low- and medium-fluence regions, it indicated a nonlinear dependence in the high-fluence region. The data reveal that the elongation efficiency of Zn is correlated with the electronic stopping power 'Se in silica' and is not correlated with either the 'Se in Zn' or the nuclear stopping power. The elongation efficiency plotted as a function of the 'Se in silica' revealed a linear relationship, with a threshold value of ∼2 keV nm(-1), which is the same dependence exhibited by the ion-track formation in silica. The log-log plot showed that the elongation efficiency increased linearly with Se above a critical value of ∼3 keV nm(-1) and steeply decreased with Se to the power of 5 below the critical Se. The steep decrease can be ascribed to the discontinuous nature of the ion tracks, which is expected at Se ∼ 2-4 keV nm(-1) in silica. The fluence Φ dependences of AR - 1 under various irradiations are well-normalized with the electronic energy deposition of SHIs, i.e., the product of Se and Φ, with a Se greater than the same critical value of ∼3 keV nm(-1). The normalized data above the critical value fell on a linear relation, AR(Φ) - 1 ∝ SeΦ, for SeΦ< 2 keV nm(-3) and a sublinear relation, AR(Φ) - 1 ∝ (SeΦ)(1/2) for SeΦ > 2 keV nm(-3). On the basis of these experimental results, we discuss some insights into the elongation mechanism.

Understanding the ion-induced elongation of silver nanoparticles embedded in silica

“…For instance, elongation of metallic nanoparticles using SHIs has been reported for cobalt NPs implanted in SiO 2 and irradiated with iodine 31 , for gold NPs implanted in planar SiO 2 films after irradiation with Si 32 and Cu 33 ions and Pt NPs formed by ion-beam synthesis in amorphous SiO 2 irradiated with Au ions 34 . More recently, there are also several works reporting the use of swift heavy ions to elongate Ag 35, 36 , Au 37–40 , Zn 41, 42 , and Ni 43 nanoparticles.…”

Fabrication of Ion-Shaped Anisotropic Nanoparticles and their Orientational Imaging by Second-Harmonic Generation Microscopy

“…Shaping of nanoparticles by a swift heavy ions beam offers unprecedented opportunities to control the properties of the particles with very high precision161718192021222324252627. This technique reshapes the particles in a way that depends on the direction of the ion beam and on the total fluence of ion irradiation.…”

Near-infrared emission in Er:ZnO thin films with embedded Si nanoparticles synthesized by ion implantation

“…The direct implantation of Si ions can be used to synthesize NPs with spherical geometries in dielectrics. By the use of swift heavy ion irradiation, the nanostructures can be reshaped, thus elongating the spherical NPs in the thin films [12][13][14][15]. The concentration of NPs can be controlled by the ion dose.…”