Morphology and plasmonic properties of self-organized arrays of ...

Chapter 4Self-organized nanoparticlearrays: optical propertiesIn this chapter, we present the optical characterizations of the specimens during all thesteps of the fabrications, from the bare LiF substrates to the 2D arrays of gold nanoparticles.4.1 Optical properties of Lithium Fluoride substratesIn this section we will focus on the characterization of the optical properties of the LiFsubstrates. As will become more clear in the next chapter, they will play an importantrole for the modelling of the optical response of the gold NP.Lithium fluoride is a well-known material for dosimetry and optoelectronics. It hasa very wide band gap of 13.6 eV, so in the visible and near-IR range it behaves like atransparent, non absorbing material (transmittance higher than 90% in the range 0.1 ÷7μm[194, 195]). Its optical characteristics have been extensively investigated mainly inconnection with its color centers [196–199]. These, usually induced by oxygen and metalions impurities, introduce weak absorptions in the 200-350 nm region [200, 201], conferringthe crystal a characteristic yellowish color.Transmittance0.950.90 [deg]8.07.57.0182181 [deg]0.856.5180123E [eV]45123E [eV]45Figure 4.1: Panel a: transmission spectrum measured at normal incidence on a doublesidepolished LiF(110) sample in the as received state. Panel b: Ψ (red curve) and ∆(black curve) spectra measured on a single-side polished LiF(110), at incidence θ = 50 ◦ .61