AVS 50th International Symposium
    Surface Science Tuesday Sessions
       Session SS-TuP

Paper SS-TuP28
Plasmons in Ag Ultrathin Films on Si(111) Studied by Energy Loss Spectroscopy with High Momentum Resolution

Tuesday, November 4, 2003, 5:30 pm, Room Hall A-C

Session: Poster Session
Presenter: T. Nagao, Tohoku University and PRESTO, JST, Japan
Authors: T. Nagao, Tohoku University and PRESTO, JST, Japan
S. Yaginuma, Tohoku University, Japan
T. Sakurai, Tohoku University, Japan
Correspondent: Click to Email
Self-organized metallic overlayers deposited on semiconducting substrates constitute an interesting class of materials since one can explore a variety of physics related to low dimensionality and size effects. The collective behavior in electron systems (plasma oscillation, or plasmon) confined in atomically thin region is expected to be very different from plasmons in three-dimension. In the present talk, we report on the thickness dependence of the plasmon dispersion curve of several- monolayers-thick Ag films supported on Si(111), by use of high-momentum-resolution HREELS. The films were prepared by "electronic growth" scheme with lateral grain size larger than 70 nm characterized by the spot profile analysis using the spectrometer in high-resolution LEED mode. In addition to the surface plasmon peak, a steeply dispersing peak was observed around the (00) Bragg spot, which rapidly decays in intensity and broadens in a very narrow momentum window of 0.04 [1/A] as a function of momentum transfer. The energy dispersion curve of this mode was explained in terms of a quasi-2D mode of thin film plasmon and its loss energy approaches the value of 1900eV which is close to the interfacial plasmon mode at the semiinfinite Ag/Si system. The details of the analysis together with the development of the spectrometer will be presented. We also plan to present some data of sheet-type plasmons in surface-state bands at silicon surfaces.