Electron-energy-loss study of clean and oxygen-exposed polycrystalline zirconium

A detailed interpretation of reflection electron-energy-loss spectra taken from clean and oxygen-exposed polycrystalline zirconium is described. Using a density-of-states model, the angular momentum character and binding energies of the unoccupied levels are discussed. Depth-sensitive oxidation state and plasmon information obtained by varying the primary electron beam energy from 100 to 600 eV is presented. The oxidation state of the zirconium appears to increase with depth through the oxgyen-containing layer suggesting that oxides such as ZrO, ${\mathrm{Zr}}_2$ ${\mathrm{O}}_3$, and possibly nonstoichiometric oxides are present.