X-ray absorption spectroscopy of size-selected, deposited small chromium clusters

Small, mass-selected Cr-n clusters soft landed onto a (1 x 1)O/Ru(001) subs trate were investigated by near-edge X-ray absorption spectroscopy. Cr-n X- ray absorption spectra exhibit size-dependent shifts of L-3 absorption edge s. Furthermore, strong cluster-substrate interaction of Cr-n clusters depos ited onto (1 x 1)O/Ru(001) results in Cr2O3-like absorption signatures and effectively inhibits diffusion and island formation even at elevated temper atures. In contrast, chromium atoms on Ru(001) have a high mobility, showin g indications of coalescence and island formation; the resulting larger clu sters can easily be oxidized. (C) 2000 Elsevier Science B.V. All rights res erved.