Free-electron-like bulk and surface states for Zn(0001)

Abstract

Energy versus momentum (kk) energy-band dispersions for s,p-like bulk and surface states of a Zn(0001) surface have been determined using angle-resolved photoemission with synchrotron radiation. We find nearly-free-electron (NFE) bulk s,p bands with an inner potential of -15.4<V0<-13.5 eV (below the vacuum level). At the zone boundary in the [0001] direction, the occupied s,p bands have a p-like critical point (3+) at -3.9 eV below EF and an s-like critical point (4-) at -2.9 eV, while the NFE final states are found at +46 eV. These NFE final states appear to have slightly different energies (2 eV) for transitions from occupied s and p states which can be described by an effective s- and p-dependent inner potential or by multiple band effects. A fully symmetric (1) s,pz-like surface state is found at -3.6 eV in the 3+-4- band gap; the band dispersion E vs kof this state has been measured over its full range of existence. The final-state lifetime broadening (24.5 eV at +37 eV and 27 eV at +54 eV final-state energies, respectively) is reflected in large widths (2-3 eV) of bulk s,p-band emission peaks. Surface-state peaks are much narrower (0.7 eV) and are limited only by initial-state lifetime broadening. © 1981 The American Physical Society.