Transition metal oxides revisited: ELNES of metal L2,3 and oxygen K edges

When examined at 0.5 eV or better energy resolution by electron energy loss spectroscopy (EELS), many inner shell loss edges begin to show new fine structures. Recently, we have been able to acquire inner shell loss spectra routinely at about 0.4 eV resolution, using the Gatan PEELS™ on the VG HB501 STEM. We have therefore decided to reinvestigate the energy-loss near-edge structure (ELNES) of oxygen K and metal L2,3 edges in first row transition metal oxides.Figure 1 shows the metal L2,3 edges from vanadium oxide, chromium oxide, manganese oxide, iron oxide, cobalt oxide, nickel oxide, and copper oxide. Except for the chromium oxide sample, which was prepared by crushing and dispersing grains of crystalline Cr2O3, samples were made by vapor-depositing a thin metal film onto rock salt, heating it in air at about 400° C while still on the substrate, and subsequently floating it off. The resultant thin oxide films were from the same sample batches as those used for the EELS Atlas, where they were identified as VOx, MnO2, Fe2O3, CoO, NiO, and CuO.