We record XPS spectra while applying 0 to +10 V or 0 to -10 V square pulses to the sample rod, which normally results in twinning of all peaks at correspondingly increased (for +10 V) or decreased (for -10 V) binding energies. For poorly conducting samples, like silicon oxide layer on a silicon substrate, the twinned peaks appear at different energies due to differential charging, which also vary with respect to the frequency of the applied pulses. Moreover, the frequency dependence varies with the thickness and can be correlated with the capacitance of the oxide layer. The technique is simple and can lead to extract important information related with dielectric properties of surface structures in a totally non-contact fashion. © 2005 Elsevier B.V. All rights reserved.