The radiative decay of plasma oscillations on nonplanar metal surfaces

We have studied the radiation resulting from electron bombardment of extremely small silver particles and of silver films containing closely-spaced, periodic surface structure. Thin silver films which were heated to a temperature slightly below the bulk-silver melting point were found to break into collections of particles with approxi-mately ellipsoidal cross sections. Electron microscopy and shadow-casting techniques were used to characterize the samples as to the distributions of particle sizes and particle shapes. The wavelength, polarization, and angular intensity characteristics of the radiation emitted by these samples were compared with the predictions of a theoretical model for the radiative decay of surface plasmons on non-spherical particles. The results indicated that two distinct modes of charge density oscillation contributed to the radiation. Very closely-spaced periodic surface modulations were produced in silver films by using the technique of electron beam lithography. Radiation resulting from the electron bombardment of these films showed evidence of structure that has been predicted theoretically. However, this structure was not well resolved. We have made suggestions which should be useful in future studies of the origin of this radiation.