(Invited) Particle Size-Dependent Photoelectron Plasmon Loss Features in Deposited Germanium Nanocrystals

The plasmon loss features of deposited and well-characterized germanium nanocrystals with average sizes of 3.5 and 4.5 similar to nm, respectively, are investigated with photoelectron spectroscopy at the Ge similar to 3d core level. We observe a particle size dependence of the surface plasmon amplitude with respect to the bulk plasmon consistent with the changing surface-to-bulk atom ratio. Additionally, the nanocrystal surface plasmons are redshifted with respect to a bulk reference by up to 0.4 similar to eV for 3.5 similar to nm particles. For the bulk plasmons no significant size dependent energy shifts can be observed for nanoparticle sizes down to 3.5 similar to nm.