Ordered Cerium Oxide Thin Films Grown on Ru(0001) and Ni(111)
Surface Science, 429 (1999) 186
Cerium oxide thin films between 1 - 10 ML thick
have been grown in situ on the
Ru(0001) and Ni(111) surfaces. The films were highly ordered with an orientation
determined by the orientation of the substrate on which they were grown as shown
by ion scattering spectroscopy (ISS) and LEED.
The principal azimuths of the oxide films were aligned parallel to the
principal azimuths of the substrates. The
lattice constant of the films was nominally the same as for CeO2
with
a fluorite structure. Optimal
films were grown by dosing metallic Ce at a rate of ca. 3 x 1014
min-1
cm-2
in an oxygen background while the substrate was at
700 K.
Fully oxidized films could be grown by using an oxygen pressure near 10-7
torr while substoichiometric films could be grown by decreasing the oxygen
pressure. The fully oxidized films were predominantly terminated by an
oxygen layer, whereas the substoichiometric films had a significant amount of
cerium in the top layer. The structure of the reduced oxide films was most
consistent with a CeO2(111) surface that contained numerous oxygen
vacancies. The films grown on
Ru(0001) were fully stable in terms of structure and composition at temperatures
up to 1000 K. The films grown on
Ni(111) lost oxygen upon annealing to 1000K.
