Surface Plasmon Excitation at Topmost Surface in Reflection High-Energy Positron Diffraction

Abstract

To investigate the excitation process of surface plasmon by fast positrons, we measured the positron energy loss spectra from Si(111)-7×7, Al(111)-1×1, and Bi(001)-1×1 surfaces under the total reflection condition using an energy-filtered reflection high-energy positron diffraction. We observed the multiple surface plasmon excitations, which can be represented by the Poisson distribution with the mean excitation number of 2.4-2.8. The energy loss spectrum is nearly independent of the glancing angle of the incident positron beam. We also measured the electron energy loss spectra at similar glancing angles and determined the mean excitation number to be 1.4-1.8. We found that due to the total reflection positrons are able to excite more surface plasmons as compared to electrons. [DOI: 10.1380/ejssnt.2010.190]