RESONANT SOFT X-RAY EMISSION SPECTROSCOPY OFV2O3,VO2andNaV2O5

Resonant soft X-ray emission (RSXE) spectra ofV2O3,VO2andNaV2O5were recorded for a series of excitation energies at resonances of the V L- and O K-absorption band. The V L- and O K-emission in these vanadium oxide bands possess considerable overlap. By resonant excitation we can tune the energy to the absorption thresholds, thereby eliminating this overlap. Hereby we obtain the V 3d and O 2p projected density-of-states of the valence band. Resonant inelastic X-ray scattering (RIXS) is found to be weak inV2O3, which we explain as being due to its metallic character at room temperature. Vanadium dioxide(VO2), semiconducting at room temperature, shows considerable RIXS features only at the O K-emission band. Distinct RIXS structures are visible in the RSXE spectra of the insulatorNaV2O5. In the emission spectra excited at the V L-thresholds of this ternary vanadium oxide, dd-excitations of the Vdxysubband at an energy loss of -1.7 eV are observed. Our observation, that RIXS is stronger for insulators than for metals, should be taken advantage of for studying insulator-to-metal transitions in vanadium compounds in the future.