Photoelectron binding energy shifts observed during oxidation of group IIA, IIIA and IVA elemental surfaces

An extensive re-evaluation of XPS binding energies (BE's) and binding energy shifts (Delta BE's) from metals, oxides and the carbonates of the group II, III and IVA elements (exceptions are Be, Mg and Hf) has been carried out using a substrate specific BE referencing approach. From From this, O-1s BE's are found to fall into surface oxide, bulk oxide and carbonate groupings, with bulk oxides showing the Iowest BE's followed by surface oxides (+similar to 1.5 eV) and then carbonates (+similar to 3.0 eV). The O-1s BE's from the bulk oxides also appear to scale with 1/d, where d is inter-atomic distance. The same is noted in the Delta BE's observed from the metallic counterparts during oxidation of the elemental surfaces. This, and the decreasing BE exhibited by Ca, Sr and Ba on oxidation is explained within the charge potential model as resulting front competing inter and intra-atomic effects. and is shown to be consistent with partial covalency arguments utilizing Madulung potentials. The Delta BE's also fall into groups according to the elements location in the periodic table, i.e. s, p or d block. These trends open up the possibility of approximating Delta BE's arising from initial and final state effects, and bond distances. (c) 2005 Elsevier B.V. All rights reserved.