Unreconstructed CdTe(100) surface prepared by ion bombardment and annealing is investigated by angle-resolved photoemission. The experimental band structure E(k_{∥}) is determined along high-symmetry lines of the surface Brillouin zone by measuring energy-distribution curves of photoelectrons. Different criteria were applied to separate surface and bulk related spectral features, e.g. calculating the position of bulk-derived emissions in the frame of the free-electron final state approximation assuming k conservation. In this way, most dispersing features could be explained. All remaining features were compared with theoretical surface band structures for different polar surface terminations which were calculated within a layer doubling procedure on the basis of an EHT-fit to the bulk band structure. The investigated CdTe(100)-(1×1) surface could be identified as Cd terminated. Two surface bands were observed, one located above the valence-band edge and the second in the open pocket of the projected bulk band structure along the Γ̅K̅ direction. At 4.6 eV binding energy an additional weakly dispersing band was found, which contains mixed surface and bulk character. The high density of bulk states associated with this edge of the heteropolar gap is also expected to contribute to this feature.
The Angle-Resolved Photoemission Electron Spectroscopy (AR PES) was applied to investigate the electronic structure of HgSe and Hg_{1-x}Fe_{x}Se crystals for (110) surface. The measured set of Angle-Resolved Energy Distribution Curves (AR EDCs) permits to determine some of the elements of the electronic band structure E(k) (energy-momentum dependence for ҐKX and ҐX directions in the Brillouin zone) for measured crystals. The Fe 3d contribution gives the states lying over the edge of the valence band of HgSe crystal (0.25 eV), and into the valence band.
The valence band structure E(k) for CdTe (111) Cd side surface 2 x 2 reconstructed was investigated along the Γ-L direction of the bulk Brillouin zone by high-resolution angle-resolved photoemission spectroscopy method in the energy range between 9.5 eV and 30.0 eV. The E(k) dependence was determined as well for bulk as for some of the surface states in the whole width of the valence band. Obtained results are compared with available calculated bulk band structure along Γ-L direction.
The phenomenon of Fano type resonant photoemission was used to distinguish the Fe electrons derived partial contribution to the valence band of a semimagnetic semiconductor Cd_{1-x}Fe_{x}Se. The states appearing at the middle of the valence band correspond to the Fe 3d electrons while the step of the density of states obtained at the valence band edge region correspondsvto the hybridized s-p-d electrons.
The synchrotron radiation in the energy range between 40 and 80 eV was applied to investigate the electronic structure of Hg_{0.7}Mn_{0.3}Se, Hg_{0.88}Fe_{0.12}Se and Hg_{0.93}Co_{0.07}Se crystals by means of the resonant photoemission spectroscopy. The set of energy distribution curves was measured in the region near the M (M = Mn 3d^{5}, Fe 3d^{6}, Co 3d^{7}) 3p-3d transitions. In order to determine thoroughly the Fano type resonance energy the constant initial states curves were measured.
The electronic structure of a new semimagnetic semiconductor (Cd,Co)Se is studied by UPS and calculated by a tight-binding version of the disordered-local-moment theory. The theory accounts for the chemical disorder and for electron interactions within the Co 3d^{7} shells. Both theory and experiment show Co 3d states deep in the valence band and also at the band edge. The last state seem to be responsible for unique properties of the Co-based semimagnetic semiconductors.
The atomic and electronic structure and interface formation of alkali metal (Na, K, Rb, Cs) and Si(100)2 × 1 surfaces is investigated by photoemission - XPS, UPS - using synchrotron radiation, scanning tunneling microscopy (STM) and by photoemission extended X-ray absorption fine structure (PEXAFS) experiments. The XPS-UPS results indicate that the alkali metal-silicon bond is a weak and polarized covalent bonding even at low coverages with adsorbate metallization at the monolayer. In contrast to III-V semiconductor surfaces, alkali metals do not induce significant structural changes of the surface: STM images performed with atomic resolution for the representative K/Si(100)2×1 systems demonstrate that, at one mono-layer coverage, the K atoms form one-dimensional linear metallic chains parallel to the Si dimers rows ⟨110⟩ direction and distant by 7.68 Å with a single site of adsorption. Below half a monolayer, the K atoms occupy various coexisting sites with no long range order. An ordering transition occurs around half a monolayer in which the adsorbate-adsorbate interaction, which was so far neglected in theoretical calculations, appears to be the leading driving force. The proposed models and concepts are discussed and compared to the latest state-of-art theoretical calculations.
JavaScript is turned off in your web browser. Turn it on to take full advantage of this site, then refresh the page.