Scandium and lutetium surfaces studied by reflection electron energy-loss spectroscopy

The reflection electron energy-loss spectra of the (1 0 0) and (0 0 1) surfaces of Sc single crystals and the (0 0 1) surface of a Lu single crystal have been studied with primary energies in the range 50–2000 eV. Scandium is congeneric with lutetium and the loss spectra of the two elements are very similar in both the collective excitations and the interband transitions. Strong excitations observed at around 41 eV are attributed to 3p → 3d and 5p → 5d transitions in Sc and Lu, respectively. The loss data of Sc fit the characteristic energy-loss data of the other elements of the first group of transition metals. Oxygen adsorption and nitrogen adsorption on the (1 0 0) surface of Sc influence the loss spectra. The observed differences are correlated with density-of-states calculations for Sc, ScO and ScN.