XPS analysis of iron aluminum oxide systems

XPS spectra of Fe2O3 and Al2O3 oxides are reported. The main emphasis is placed on the quantitative analysis of Ar+ ion reductive effects on Fe2O3 surfaces in terms of no/nFe atomic ratios achieved by use of the “First Principles Model”. No Fe metal is found in etched Fe2O3. Quantitative results show that the reduction: Fe2O3 → 2 FeO+12O2 occurs in the etching conditions used. Evidence of this reduction is found in the photoelectron spectra of the pure oxide as well as in those of Fe2O3+Al2O3 mixtures. A quantitative approach is proposed to derive Ar+-induced modifications at Fe2O3 surfaces in the mixtures. This approach permits the derivation of no/nFe changes on the basis of intensity ratio measurements IO(Al)/IO(Fe) between the two oxide components in the O 1s band of the mixtures. The correlation of derived nAl/nFe atomic ratios is very high in a vast range of composition of the mixtures analyzed either in the as received condition and in the etched condition. A sensitivity factor for the Fe 2p32 transition is given: SFe2p32 = 2.50 (with respect to SF1s taken as the unity), which applies to the VG Esca 3 MkII apparatus used in this work. Comparison with previous quantitative XPS analysis of Fe2O3 and Al2O3 is presented.