Angle-resolved ultraviolet photoemission spectroscopy measurements have been made from the (0001) and (112̄0) surfaces of magnesium in the photon energy range of 15 to 115 eV. Both bulk and surface features are identified. The occupied bands along the  direction are characterized by the measured energy eigenvalues at the Γ point: Γ1+=6.15±0.1 eV, Γ3+=1.7±0.1 eV, and Γ4-=0.9±0.1 eV. The bandwidth, as measured for both the (0001) and the (112̄0) surfaces, is 10% smaller than that predicted by band-structure calculations, while the Γ3+-Γ4- band gap is twice as big as calculated. The narrower experimental bandwidth is related to the fact that the excitation spectrum of the system is measured, while the origin of the wider experimental gap is not as clear. The final states higher than 28 eV above EF are well described by a free-electron band of effective mass m*/m=1.04, originating 6.15 eV below the Fermi level, while the low-energy final states deviate greatly from free-electron-like behavior. The peak widths of the bulk features in both the  and the [112̄0] direction are significantly larger than predicted by interacting electron-gas theory. The peak widths along  increase near the middle of the band, due to final-state effects. The binding energy of the Γ̄ surface state on the (0001) surface has been redetermined to be 1.6±0.1 eV. A surface state at M̄ has a binding energy of 1.1±0.1 eV. The Γ̄ surface state shows a sharp intensity resonance near Latin small letter h with strokeω=44 eV giving the location of a state of Γ4- symmetry in the final state. The M̄ surface state shows a similar resonance near Latin small letter h with strokeω=26 eV. The surface-state dispersions have been measured in the Γ̄-M̄ direction.
ASJC Scopus subject areas
- Condensed Matter Physics