On energy transfer processes at cluster–oxide interfaces: silver on titania

Using a scanning tunneling microscope, electron-stimulated photon emission spectra have been measured for individual Ag clusters on differently pretreated TiO2(1 1 0) substrates. For clusters on weakly reduced TiO2, we observe radiating decays of Mie-plasmons shifting to higher energies as cluster sizes decrease. On strongly reduced TiO2, plasmons are dissipated via energy transfer to electron–hole pair excitations in the oxide and emission spectra reveal radiating decays of TiO2 excitons.