Interaction of O₂, CO and CO₂ with Co films

Abstract

Metastable impact electron spectroscopy (MIES), ultraviolet photoelectron spectroscopy (UPS(HeI)) and x-ray photoelectron spectroscopy (XPS) were applied to study the interaction of O 2 , CO and CO 2 with Co films at room temperature. The films were produced on Si(100) surfaces under the in situ control of MIES, UPS and scanning tunnelling microscopy (STM). For O 2 , dissociative adsorption takes place initially and then incorporation of oxygen starts at exposures of ∼5 L. Comparison of the MIES and UPS spectra with those published for CoO shows that near-stoichiometric CoO films can be obtained by co-deposition of Co and O 2 . The CO is adsorbed molecularly up to a maximum coverage of ∼0.6 monolayer, with the C-end pointing towards the surface. The CO 2 adsorption is dissociative, resulting in the formation of Co-CO bonds at the surface. The resulting oxygen atoms are mostly incorporated into the Co layer. For all studied molecules the interaction with Co is similar to that with Ni.

Oxygen adsorption on ultrathin Co/Ir(111) films: Compositional anomaly

“…The complex adsorption kinetics should contain the possibility to incorporate oxygen into the film. The incorporation of oxygen in Co has been reported recently for oxygen exposure on Co/Si(1 0 0) films [15]. Moreover, the formation of different oxidation states at various substrate temperatures was revealed for oxygen on Co/W(1 1 0) films [16].…”

“…Iridium is therefore an excellent substrate giving the possibility for manipulating the oxidation process of clusters and films on it. By increasing the oxygen exposure of Co films supported on a Si(1 0 0) surface, the dissociative adsorption followed by incorporation of oxygen has been recently reported [15]. Moreover, modifications of surface magnetism, depending on the chemical state of oxygen, have been reported for oxygen exposed Co/W(1 1 0) films [16].…”

Study of the structure and stability of cobalt nanoparticles for ferrofluidic applications

“…These films were then exposed to O 2 , CO, and CO 2 , again under in situ control of MIES/UPS. A detailed presentation of the results will be the subject of a future publication; 19 only a short summary will be presented here. Briefly, formation of Co-O bonds during the film oxidation produces MIES/UPS spectra that are very similar to those for the corresponding O-Ni system.…”

“…3. The identification of the emission seen between 0 and 5 eV as due to ionization of 3d Co 2+ states 19 is of particular importance for the interpretation of the spectra from the pre-stabilized and the peptized cobalt particles. CO adsorbs molecularly, manifesting itself in two peaks 5σ ; 1π (7.5 eV) and 4σ (10.7 eV) (Fig.…”

Formation and Characterization of Pt Nanoparticle Networks

“…A detailed presentation of the results and their interpretation can be found elsewhere. [34] Secondly, pre-stabilized Co nanoparticles were deposited on SiO x substrates from suspensions in toluene. [35] STM indicated that a closed layer of the particles was obtained.…”