Low-energy electron-loss spectroscopy of a ZnSe(111) surface

Energy-loss spectroscopy of the ZnSe(111) surface, cleaned by ${\mathrm{Ar}}^{+}$ bombardment and annealing under ultrahigh-vacuum conditions, has been studied at primary electron energies $E_p$ from 30 to 250 eV. In addition to bulk-related transitions including bulk interband transitions, bulk- and surface-plasmon excitations, and transitions from Zn and $\mathrm{Se} 3d$ bands to conduction bands, several surface-related transitions have been observed. The loss spectrum changes its shape drastically with primary electron energy in the region $E_p=60\mathrm{}-115$ eV. Both at $E_p\lesssim 60 \mathrm{eV} \mathrm{and}\gtrsim 200 \mathrm{eV}$ the spectrum is rather surface independent. The spectrum at $E_p\lesssim 60$ eV may be described by the bulk characteristic loss function. The surface-related transitions are remarkable, in particular, at $E_p\simeq 100$ eV. The surface-related transitions at 5.7, 12.5, and 14.3 eV are assigned as the transition to the Zn dangling bond state, the transition from the Se back bond state, and the transition from the $\mathrm{Zn} 3d$ band to the Zn dangling bond state, respectively.