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 separat
e UHV-systems either by vapor deposition (PVD) or by pulsed laser abla
tion (PLA). The oxygen saturation exposure depends on the preparation
method: in PVD-films at least 100 L are needed, while in films deposit
ed by PLA only 10 L are required. However, films prepared by PLA, but
on cleaved muscovite, showed uptake curves saturating at approximate t
o 80 L as in evaporated films. The work function changes upon oxygen a
dsorption showed an initial increase of 0.2 eV, followed by a steep de
crease, saturating at approximate to - 1.2 eV. An oxide formation is c
learly demonstrated by the AES MVV spectra of Co at exposures above 9
L. (C) 1997 Elsevier Science Ltd.