Figure 2. Nonlinear excitation properties of single hot spots of Tollens silver films in three distinct regimes of surface coverage and morphology.

For each film, the distribution of resonance widths (Column A), polarization anisotropy values (Column B) and in-plane dipole angles (Column C) are shown. Representative excitation spectra of single hot spots are inset in Column A; SEM micrographs of the substrates are given in Column C. At low surface coverage (Row I) the films consist of well-separated silver nanoparticles. Increased surface coverage leads to films that are made up of interconnected silver islands (Row II) and are ultimately semicontinuous (Row III). The distribution P of anisotropy values is bimodal, corresponding to unpolarized and polarized hot spot excitation. The distribution of phase angles arises from hot spots which can be excited by either p- or s-polarized light, the number of which is described by N.