Use and limitations of electron flood gun control of surface potential during XPS: two non homogeneous sample types

The ability of charge compensation methods to control surface potential is examined for two types of non-homogenous samples: a small conducting dot on an insulating substrate and an insulating thin film on a conductive substrate. Results demonstrate that two newer types of charge compensation systems have improved performance in relation to some previous flood-gun, systems, while reaffirming the concept that a primary objective of charge compensation is to find conditions for which the surface potential of the specimen is as uniform as possible. However, experiments,involving both flood gun use and specimen grounding demonstrate that peak broadening and shifting can occur when two (or more) potentials are present in the region of analysis. Finally,. the ability of interface charge to shift specimen potentials and measured binding energies demonstrates fundamental limitations to the absolute accuracy of binding energy measurements, but also remind us that charging phenomena can be used to obtain important information about the sample. Copyright (C) 2002 John Wiley Sons, Ltd.