PLASMON BEHAVIOR OF ZN FROM ELECTRON-ENERGY-LOSS SPECTROSCOPY

The momentum-dependent dielectric function of Zn was measured using el ectron loss spectroscopy (EELS) in transmission. The loss function in the low-energy region is found to be a superposition of a sharp absorp tion feature due to the excitation of electrons from the 3d level at a binding energy of 9.4 eV and a broad not well pronounced feature at a bout 14 eV, which is attributed to the collective plasmon excitation o f the free charge carriers. This latter feature becomes more pronounce d with increasing momentum transfer due to a strong decrease of the co re-level oscillator strength. The decrease of oscillator strength lead s to an initially vanishing dispersion of the plasmon, and to a reduct ion of the plasmon line width with increasing momentum transfer. This behavior can qualitatively be understood in the framework of a Drude-L orentz approach. [S0163-1829(97)06540-5].