Interaction of oxygen with chromium deposited on Al2O3/NiAl(1 1 0)

We have investigated the growth and reactivity of chromium layers deposited onto a thin alumina film at room temperature and at 570 K. The interaction between Cr and the Al2O3/NiAl(1 1 0) surface leads to partial oxidation to Cr2+ and Cr3+ species. Complete oxidation to Cr3+ was achieved using moderate O2 doses at room temperature in vacuum. Cr has also been deposited in an O2 background pressure of 1.4 × 10−6 Torr. The development of the XP spectra after deposition in O2 suggests that chromium oxide catalyzes the oxidation of aluminum atoms below the thin otherwise inert alumina film. Our results also show that deposition of chromium on Al2O3/NiAl(1 1 0) at 570 K leads to significantly larger clusters than at room temperature as indicated by the incomplete oxidation of Cr.