Electron-energy-loss study of the mercury chalcogenides

Electron-energy-loss measurements have been made on crystals of HgSe, HgTe, and hexagonal HgS over the energy range 0--50 eV by reflection techniques. The measurements were made using electron-beam energies of 250 to 1000 eV from surfaces obtained by cleavage in ultrahigh vacuum. The resulting spectra showed structure dependent upon surface condition at 8.9, 9.1, and 8.1 eV in HgS, HgSe, and HgTe, respectively. This structure has been associated with surface plasmon excitation. Bulk plasma peaks were observed at 20.8, 17.2, and 14.7 eV and d-band transition peaks at 12.3 and 14.1 eV, 10.2 and 12.2 eV, and 10.2 and 11.8 eV, respectively, for HgS, HgSe, and HgTe. The large splitting of these latter peaks allows unambiguous identification as d-band transitions. The energies obtained from the energy-loss spectra are compared to those obtained from optical reflectivity and x-ray and uv photoemission