Figure 11.

Characterization of Heterojunction Plasmons. (a) Deposition of Ag onto TiO₂ is shown to enhance 2PP yields and consequently modifies the spectra of the s- and p-polarized excitations. The work function of the sample is noted to decrease around 0.35 eV, shifting the onset photoemission energy. (b) The 2PP yields are determined by integrating the photoelectrons counts with respect to the final photoelectron energy E_f and are plotted as a function of the change in the work function, which is dependent on the depth of Ag coverage. (c) A schematic portraying the enhancements of the 2PP yield with respect to the incident laser wavelength polarization and crystal azimuth orientation. p-polarized light has both the parallel and perpendicular electric field components, while the s-polarized light consists only of the parallel component. (d) Wavelength dependence of the 2PP enhancement by the parallel and perpendicular plasmon modes at energies 3.1 and 3.8 eV. This is determined by taking the ratio of p- to s-polarization yields (right y axis) and Ag/TiO₂ to Mo (a polycrystalline Molybdenum sample that assumes a flat spectral response) yields. Reprinted with permission from Ref [161] Copyright Springer Nature (2017).