Oxygen adsorption on thin cobalt films. An Auger and work function study

The adsorption of oxygen by thin cobalt films supported on oxidized Si(100) was studied at 300 K using Auger electron spectroscopy (AES) and work function changes (Delta phi). The films were prepared in separate UHV-systems either by vapor deposition (PVD) or by pulsed laser ablation (PLA). The oxygen saturation exposure depends on the preparation method: in PVD-films at least 100 L are needed, while in films deposited by PLA only 10 L are required. However, films prepared by PLA, but on cleaved muscovite, showed uptake curves saturating at approximate to 80 L as in evaporated films. The work function changes upon oxygen adsorption showed an initial increase of 0.2 eV, followed by a steep decrease, saturating at approximate to - 1.2 eV. An oxide formation is clearly demonstrated by the AES MVV spectra of Co at exposures above 9 L. (C) 1997 Elsevier Science Ltd.