THE VALIDITY OF C1S CHARGE REFERENCING IN THE XPS OF OXIDIZED AL-SI ALLOYS

During a XPS study of oxide growth and segregation on commercial alumi nium-silicon alloys, problems were encountered in the application of C 1s charge referencing. Using the C1s peak maximum as a reference, shif ts were observed in the aluminium and magnesium peak positions, partic ularly after high temperature oxidation, which could not be accounted for. Referencing against the native oxide O1s peak corrected the shift s. A consequent analysis of the C1s spectra revealed that the hydrocar bon contamination was reacting under the conditions used to oxidise th e alloys. From the XPS results it is deduced that active sites on the oxidised alloy surface are responsible for catalytic cracking and oxid ation of the adventitious hydrocarbon. Parallel studies on other heat treated oxidic systems have produced similar results. It is recommende d that an alternative to C1s charge referencing should be used when pe rforming XPS studies on heat treated oxidic systems.