Speaker
Description
In this presentation, the linear dynamics of ultrathin oxide films and oxide surfaces in the range from 1 to 50 THz upon electromagnetic excitation will be discussed. Surface vibrational spectroscopy based on high-resolution electron energy loss spectroscopy (HREELS) reveals the full dielectric characterization of the surface response of BaTiO$_3$, SrRuO$_3$, and SrTiO$_3$ with different intentional doping levels. The extracted surface dielectric function will be quantitatively compared with available bulk infrared data and allows the experimental determination of the surface-near doping level in oxides. HREELS data allow for the first time the determination of the complex dielectric functions of ultrathin oxide films down to single unit cell thicknesses. These data are discussed with respect of possible two-dimensional electron gases at the surface, electron-phonon coupling, as well as strain-driven phonon softening.
Support by the Sonderforschungsbereiche SFB-762 “Functional Oxide Interfaces” (projects A3 and B8) and SFB/TRR-227 “Ultrafast Spin Dynamics” (project A6) is gratefully acknowledged.
