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, M gO, and MgAl2O4. It is found that both SXE and SXA are sensitive to th e crystal phase, suggesting their use as a structural probe. Compariso n of the Al L2,3 SXE of alpha-Al2O3 and the Mg L2,3 SXE of MgO with lo cal-density-approximation (LDA) density-of-states calculations shows t hat the agreement is good, and suggests that the final-state rule is v alid 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 Mg O SXA spectrum well. Evidence which suggests that the remaining featur es are due to band structure is given.