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

Energy-loss spectroscopy of the ZnSe(111) surface, cleaned by Ar⁺ bombardment and annealing under ultrahigh-vacuum conditions, has been studied at primary electron energies Eₚ 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 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 Eₚ=60-115 eV. Both at Eₚ60 eV and200 eV the spectrum is rather surface independent. The spectrum at Eₚ60 eV may be described by the bulk characteristic loss function. The surface-related transitions are remarkable, in particular, at Eₚ100 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 Zn 3d band to the Zn dangling bond state, respectively.