A total current spectroscopy study of metal oxide surfaces: I. Unoccupied electronic states of ZnO and MgO

Abstract

Unoccupied density of states (DOS) for the polar (0001) Zn, (000 1) O and non-polar (10 10) ZnO surfaces and for a MgO(001)-c(2 × 2) thin film were studied using total current spectroscopy (TCS). TC spectra of the ZnO surfaces reveal the Zn 4s-O 2p band (6.2 eV) and two DOS maxima in the Zn 4p-O 2p band which exhibited different energy positions on the Zn-terminated (8.1 eV) and O-terminated (11.0 eV) surfaces. In the TC spectra of the MgO thin film, the energy location of Mg-derived (8.0, 14.8 and 21.0 eV) and O-derived (11.6, 14.2 and 18.5 eV) maxima of DOS were determined. Previously reported data on DOS of these materials is discussed, and it is shown that additional detailed information on the energy structure of unoccupied DOS in ZnO and MgO in the 5-25 eV range above E F has been found.

Alkali-Metals on ZnO(10-10) Studied by Low-Energy Electron Diffraction and Photoelectron Spectroscopy

“…The clean surface thus prepared gave a sharp (1×1) LEED pattern. The work function of the clean surface was typically 4.5-4.9 eV, in good agreement with the literature values of 4.64-5.05 eV [10][11][12].…”

Exciton and core-level electron confinement effects in transparent ZnO thin films

“…Moreover, feature A is more peaked in the TEYN spectra indicating that it is more sensitive to surface states. Feature A has been proposed to be associated to σ-type interaction between Zn and O planes27. Modification of its intensity and energy can be related to surface relaxation phenomena.…”

“…In contrast, the spectra corresponding to the film of lowest thickness exhibit increased and decreased intensity of the B and A contribution with reference to the thickest films, respectively. The high amplitude of feature B indicates the surface is (0001) O-terminated2728. The much weaker amplitude of feature A indicates a lower hybridization of Zn and O atoms.…”

F-doping of nanostructured ZnO: a way to modify structural, electronic, and surface properties

“…The latter is even more pronounced for ZnO. 43,44 Following the dipole-transition selection rule, 45 the features in the O K-edge spectra (Fig. 12(a)) are excitations related from O 1s to Fig.…”