Electron density of states at the edge of the valence band of Cd 0.88Fe 0.12Se—A photoemission yield study

Abstract

The electronic structures of Cd 0.88Fe 0.12Se and CdSe have been investigated by photoemission yield spectroscopy (PYS) in the photon energy range from 5 to 12 eV. The ( 11 2 ¯ 0 ) surfaces were obtained by cleavage under ultrahigh vacuum (UHV) conditions. An Fe-related emission appeared at 0.58 eV above the valence band edge. The freshly cleaved surface of Cd 0.88Fe 0.12Se interacted with ambient atmosphere more strongly than CdSe crystal. Leaving the sample in an UHV chamber at room temperature enabled us to identify surface related features and to observe decrease of the ionization energy E i, energy threshold E d and the crystal affinity χ due to change of the surface conditions. Effective density of states, derived from the experimental spectra of Cd 0.88Fe 0.12Se exhibits, in contrast with CdSe, a surface-related feature degenerated with the bulk valence band.