Low-energy electron energy loss spectroscopy on CaF2(111) surfaces

CaF2(111) surfaces were studied by Auger electron spectroscopy and electron energy loss spectroscopy (EELS). A clean stoichiometric surface was achieved by heating samples under an ultrahigh vacuum at 600 deg C. A new peak in the EELS spectrum was observed in the band gap region, which may be ascribed to surface excitation. Peaks whose intensity strongly depends on the incident electron energy were observed in the region of core-electron excitation. These peaks seem to come from the optically forbidden transitions. (author)