Electronic band structure of magnesium and magnesium oxide: experiment and theory

Abstract

Electron momentum spectroscopy (EMS) has been used to measure the valence band electronic structure of thin magnesium and magnesium oxide films. The band structures have also been calculated within the linear muffin-tin orbital (LMTO) approximation. The free-electron-like parabola characteristic of metallic solids was observed for magnesium with a bandwidth of approximately 6 eV, in agreement with previous measurements. The inclusion of energy broadening due to finite hole-lifetime effects and a Monte Carlo simulation of multiple scattering events gives good agreement between calculated and measured band structures. However, we measure a much higher intensity due to plasmon 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 completely absent in the experimental spectra for magnesium oxide. The LMTO calculation reproduces the overall structure and dispersion range of the oxide. The measured and calculated energy gap between upper and lower valence bands and their relative intensities do not agree quantitatively. This discrepancy may be due to a contribution of magnesium s states to the predominantly oxygen p states in the upper band.

Electronic band structure of calcium oxide

“…Hence there is a shift of about 2 eV in positions of the corresponding p-band peaks. A similar increase of the experimental bandgap was observed in our previous measurements of MgO [31] and BeO [51]. This discrepancy seems to be due to the failure of the LDA approximation to correctly describe electron correlation effects in insulating solids.…”

“…The theory changes from 0.2 to 1.6 over the same momentum range. We observed a similar disagreement in the relative p-to -s-band EMD ratio for MgO [31] and BeO [51,52].…”

“…We followed the target preparation technique used for MgO [31]. Calcium (99% pure) was formed layer is determined on the basis of providing a complete coverage of the am-C substrate surface and not so thick that multiple scattering dominates.…”

“…EMS can provide a direct measurement of electron distribution in energy-momentum space, and has been applied to a variety of targets in gaseous [28,29] and solid [30,31,32,33] forms. EMS allows us to directly observe the dispersion relationship in solids, and also measure band intensities, i.e.…”

Nonlinear optical response of Mg/MgO structures prepared by laser ablation method

“…Canney et al studied electronic band structure of thin magnesium and magnesium oxide films, experimentally and theoretically. They showed that the investigated band structures of Mg and MgO have the characteristic of a metallic and ionic solid, respectively [19]. Phuoc et al synthesized Mg/MgO nanocrystallites by laser ablation of magnesium in acetone and isopropanol with a Q-switched Nd-Yag laser operating at 1064 nm and investigated structural properties of the formed Mg/MgO nanostructures [20].…”