Unoccupied states evolution with oxidation of ultrathin Mg, Zn and Cd layers on SrTiO3(100) surfaces

An unoccupied density of states (DOS) evolution under oxidation of ultrathi n Mg, Zn and Cd layers on SrTiO3(1 0 0)-(2 x 2) substrates are investigated . The metal deposition and subsequent oxidation were studied in situ under UHV conditions by means of LEED, AES, TCS and work function measurements. A n appearance of metal- and oxygen-derived bands of the unoccupied DOS was t raced in the TC spectra. Metal oxidation was followed by the hybridization of metal and oxygen orbitals and by the appearance of the mainly O 2p oxyge n-derived bands, which are characterized by a set of DOS maxima, located at the following energies (above the Fermi level): 8.0, 11.5, 14.3, 15.0 and 19.0 eV for MgO; 6.0, 8.1, 16.8 and 20.5 eV for ZnO and 7.5, 10.0 and 12.7 eV for CdO. The results obtained are discussed in comparison with previousl y published experimental and theoretical data on unoccupied DOS in metal ox ides. (C) 2001 Elsevier Science B.V. All rights reserved.