Enhanced peak separation in XPS with external biasing

We have demonstrated that the Au 4f peaks of the capped gold nanoparticles deposited on a SiO2 (20 nm)/Si substrate can be separated form the Au 4f peaks of a gold metal strip, in contact with the same sample, by application of an external voltage bias to the sample rod while recording the XPS spectra. The external bias controls the flow of low-energy electrons falling on to the sample which in-turn controls the extent of the differential charging of the oxide layer leading to shifts in the binding energy of the gold nanoparticles in contact with the layer. The method is simple and effective for enhancing peak separation and identification of hetero-structures.