Role of surface and bulk plasmon decay in secondary electron emission

The mechanism of secondary electron emission by impact of 100-eV electrons on an Al(100) surface has been investigated by measuring the secondary electron spectrum in coincidence with loss features in the spectrum of reflected electrons. Distinct peaks are observed at energies corresponding accurately to the surface and bulk plasmon energies minus the work function of the analyzer, demonstrating that plasmons excited by electron energy losses predominantly decay via creation of single-electron-hole pairs that act as a source for the secondary electron spectrum. These findings suggest a mechanism for emission of secondary electrons very similar to photoelectron (PE) emission, the difference being the step leading to electron liberation, i.e., plasmon decay in the present case versus photoionization in the case of PE.