Surface-plasmon excitation by electrons in microlithographically produced channels

Energy-loss spectra have been measured for low-energy (900 eV) electrons transmitted through cylindrical microchannels in silver foils. Arrays of such channels were produced by a microlithographic process. Inelastic scattering of the electrons results in a peak in the energy-loss spectrum in the vicinity of the silver surface-plasmon energy. The probability of surface-plasmon excitation was measured as a function of incident-beam angle and compared with theory. The results indicate that inelastic scattering occurs principally in a narrow region close to the metal surface where roughness features are important. Calculations in which these roughness structures are modeled as small spheres give excellent agreement with the measured shape and position of the energy-loss peak.