X-RAY-INDUCED BEAM DAMAGE OBSERVED DURING X-RAY PHOTOELECTRON-SPECTROSCOPY (XPS) STUDIES OF PALLADIUM ELECTRODE INK MATERIALS

The surface compositional characteristics of two palladium metal electrode inks, air-dried on barium titanate (BaTiO3) dielectric ceramic substrates, have been studied using x-ray photoelectron spectroscopy (XPS). It is found that exposure of the inks to the x-ray beam during the time of analysis required for data acquisition causes surface damage. Changes in the C 1s and O 1s regions in particular, which reflect modifications to the organic, polymeric binder materials present in the inks, have been investigated as a function of x-ray exposure time, incident photon energy and beam power levels. Additional complexity in the C 1s spectral envelope that cannot be explained in terms of the expected contributing organic functionalities is observed. This is explained in terms of a difference in charging effects experienced by adventitious carbon species and those intimately associated with palladium metal centres. The degree of damage induced by the x-ray beam under specific operating conditions has been compared also with that caused by exposure of the surfaces to an electron beam. Indications of the time scales and operating parameters for conducting XPS experiments on the unmodified surface, prior to surface degradation, are given.