Abstract
We analyze the effect of contaminants on the quadrupolar magnetic, dipolar electric and dipolar magnetic resonances of silicon nanoparticles (NPs) by considering the spectral evolution of the linear polarization degree at right angle scattering configuration, P L (90°). From an optical point of view, a decrease in the purity of silicon nanoparticles due to the presence of contaminants impacts the NP effective refractive index. We study this effect for a silicon nanosphere of radius 200 nm embedded in different media. The weakness of the resonances induced on the P L (90°) spectrum because of the lack of purity can be used to quantify the contamination of the material. In addition, it is shown that Kerker conditions also suffer from a spectral shift, which is quantified as a function of material purity.
Highlights
Nanotechnology has revolutionized science over the last several years, generating important theoretical and practical developments
In order to obtain the dielectric constants of contaminant materials, we consider contaminants homogeneously distributed by using a weighted average[15], in which we have varied the Si concentration from 99.0% to 100.0%, while the concentration of the main metallic contaminants, considered as Fe, Al and Ti, is kept in the initial proportion of most commercial samples[16]
We test the results of these Effective medium theories (EMTs) and find deviations smaller than 5% for these cases of very small amounts of contaminants
Summary
Nanotechnology has revolutionized science over the last several years, generating important theoretical and practical developments. Under certain conditions of the electric permittivity ε and magnetic permeability μ, proposed by Kerker et al[7,8], the forward and backward scattered intensity is almost null or null respectively. The resonances depend on the size, shape and optical properties of the NPs. For a given material, resonances are red-shifted as NP size increases, and they are influenced by the refractive index of the surrounding medium, mmed. The linear polarization degree of light scattered perpendicular to the incident beam, PL(90o), is a polarimetric parameter that contains information about the magnetic or electric response of the resonances[11,12] It can be used for determining the NP size and mmed, which makes it a promising tool for sensing applications[13].
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