Cobalt oxide nanolayers on Pd(100): The thickness-dependent structural evolution

Abstract

The growth of interface-stabilized cobalt oxide (CoO x) nanolayers on Pd(100) has been investigated and their structures are reported as a function of coverage. Several different phases have been observed by LEED and STM experiments, and they have been characterized spectroscopically by photoemission and X-ray absorption. The data indicate that in the low coverage regime (up to Θ Co ≈ 2–3 ML) rock-salt CoO type phases are formed (defective in the single layer regime, and stoichiometric in multilayers) with (100) or (111) termination. At higher coverage (Θ Co ≈ 10–20 ML) spinel Co 3O 4(111) and CoO(100) layers have been detected, in ratios dependent on the preparation conditions. The observed structures are discussed in relation to similar structures reported recently for CoO x films on Ir(100) [W. Meyer et al., J. Phys.: Condens. Matter 20 (2008) 265011].