SOFT-X-RAY INVESTIGATION OF MG AND AL OXIDES - EVIDENCE FOR ATOMIC AND BAND-LIKE FEATURES

Soft-x-ray emission (SXE) and soft-x-ray absorption (SXA) are used to investigate the electronic structure of alpha-Al2O3, anodized Al2O3, MgO, and MgAl2O4. It is found that both SXE and SXA are sensitive to the crystal phase, suggesting their use as a structural probe. Comparison of the Al L2,3 SXE of alpha-Al2O3 and the Mg L2,3 SXE of MgO with local-density-approximation (LDA) density-of-states calculations shows that the agreement is good, and suggests that the final-state rule is valid for the SXE of these oxides. On the other hand, comparisons show that results of the SXA and LDA calculations are not in good agreement. A model based on atomiclike excitations explains a portion of the MgO SXA spectrum well. Evidence which suggests that the remaining features are due to band structure is given.