Sn-doped In 2 O 3 (ITO) nanoparticles with various Sn doping concentrations were successfully fabricated using a liquid phase coprecipitation method. Similar to sputtered ITO thin films, Sn doping reaches a maximum carrier density (1.52 × 10 21 cm - 3) at 10 at. % in ITO nanoparticles, which was estimated from the bulk plasmon energy based on a scanning ellipsometry (SE) simulation. Interestingly, the X-ray photoelectron emission spectra (XPS) of In 3d core levels show a clear asymmetric peak with a shoulder on the high-binding-energy side for degenerated ITO nanoparticles, which may be associated with the influence of the surface plasmon or plasmonic coupling. Our results suggest that combining the SE simulation and XPS measurements effectively provides a new way to understand the difference between bulk plasmons and surface plasmons for transparent conductive oxide nanoparticles.
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