Electronic band structure of magnesium and magnesium oxide: experiment andtheory

Electron momentum spectroscopy (EMS) has been used to measure the valence b and electronic structure of thin magnesium and magnesium oxide films. The b and structures have also been calculated within the linear muffin-tin orbit al (LMTO) approximation. The free-electronlike parabola characteristic of m etallic solids was observed for magnesium with a bandwidth of approximately 6 eV, in agreement with previous measurements. The inclusion of energy bro adening due to finite hole-lifetime effects and a Monte Carlo simulation of multiple scattering events gives good agreement between calculated and mea sured band structures. However, we measure a much higher intensity due to p lasmon excitation compared with the simulated intensity. Upon oxidation the valence structure splits into two distinct, less dispersive bands typical of an ionic solid. Intensity due to plasmon excitation was almost completel y absent in the experimental spectra for magnesium oxide. The LMTO calculat ion reproduces the overall structure and dispersion range of the oxide. The measured and calculated energy gap between upper and lower valence bands a nd their relative intensities do not agree quantitatively. This discrepancy may be due to a contribution of magnesium s states to the predominantly ox ygen p states in the upper band.