Oxidation and growth of ME thin films on Ru(001)

The oxidation and growth of ultra-thin Mg films on a Ru(001) substrate have been studied using X-ray photoelectron spectroscopy (XPS) and thermal deso rption spectroscopy (TDS) in the temperature range of 300-1500 K. Our resul ts suggest that the growth of Mg thin films follows a layer-by-layer mode. Upon oxygen adsorption at 300 K, two O 1s peaks were detected on the Mg fil m. The peak at 532.2-532.6 eV could be attributed to either dioxygen or par tially reduced species (Odelta-, delta < 2), whereas that at 530.1-530.6 eV is due to lattice oxygen in MgO. Annealing of the oxidized film to 800 K c auses the conversion of the dioxygen or partially reduced species to the ox ide state. Thermal desorption peaks of MgO were directly detected at 1000-1 127 and 1350-1380 K, respectively. However, initial evaporation of Mg atoms onto an oxygen pre-adsorbed surface yields a fully oxidized MgO. Further M g deposition results in the formation of a partially oxidized film with the observation of an O 1s peak at 532.2 eV. (C) 1999 Elsevier Science B.V. Al l rights reserved.