Resolving structure dimension for SiO2@C Core-shell nanoparticles by three-step modeling of ellipsometry

The ellipsometry is used to characterize the dimensions of SiO2@C core–shell nanoparticles (397 ± 19 nm) by coating on the substrate with different core diameter and coverage. Three-step modeling has been utilized to resolve the surface coverage, SiO2 core diameter and C-shell thickness. It is found that the ellipsometry can directly extract the SiO2 core diameter as the function of the core etching time, but with unchanged C-shell thickness (38 ± 1 nm). This derivation has been demonstrated to be independent of the coverage and consistent with the statistical value from TEMs and SEMs. For low coverage, the volume ratio derived from the ellipsometry is consistent with the surface area ratio of nanoparticles statistically measured by SEMs. Also the substrate impacts the dielectric properties for nanoparticles and C-shell in whole spectrum due to the image dipole effects. The three-step modeling of ellipsometry shows a method to characterize each part dimensions of core–shell structure.