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

4.2. OPTICAL PROPERTIES OF AU NANOPARTICLES ARRAYS 71and the height of the particles as the dimensions along and across the ripples and normalto the surface, respectively.Dependence of LSP modes on ripple periodicityWe first investigate the influence of the ripples periodicity on the position of the plasmonicresonances. In fig. 4.11 we report sets of reflectivities measured on several arrays of inplanespherical particles at 50 ◦ of incidence. In all cases ≈5 nm of gold were deposited,and the samples have different periodicities of the underlying ripple structure: Λ ≈ 30 nmfor black lines (sample in fig. 3.8(a)), Λ ≈ 35 nm for blue lines, and Λ ≈ 40 nm for redlines (sample in fig. 3.8(b)).psps = 30 nm = 35 nm = 40 nm0.04R P||L modeER S┴0.30R P0.020.20RS0.100.004006008001000a. [nm] [nm] b.40060080010000.30R S||T modeR p┴0.03R S0.20E0.02RP0.100.014006008001000c. [nm] [nm]d.Figure 4.11: Sets of reflectivities at θ = 50 ◦ incidence, for s- and p-polarized incidentlight, measured on nanopatterned LiF(110) samples with different periodicities Λ, afterthe deposition of t Au = 5 nm Au at T ≈ 100 ◦ C and annealing at T = 400 ◦ C. Plane ofincidence parallel (left panels) and perpendicular (right panels) the ripples. Excitation ofLSP L mode (panels a, b) and T mode (panels c, d).For decreasing Λ, we observe two main variations of the resonances: both the L andT modes shift towards longer wavelengths, the L mode shifting from λ ≈ 580 nm for4006008001000