Practical Aspects of Charging Phenomena in XPS as demonstrated in Oxidized-Al Films on Al and Al Alloys

Understanding the surface and interface structure, composition and chemistry of insulating materials has long been of importance in surface analysis. The relevance of insulating surfaces to the environment, and the increasing use of newer and more complex oxide films in electronic and optical applications significantly increases the information needed about these materials. Through a series of examples using Al-oxide films, this paper summarizes some conceptual and practical issues related to analysis of insulators, including vacuum-level and Fermi-level referencing, charge buildup at interfaces, the use of charge neutralization, the impact of electron and ion-beam damage, and the influence of impurities on oxide properties and measurements. Many of the measurements are understood through consideration of potential variation through a specimen. Current results, along with many in the literature, demonstrate that surface charging is not a problem that can be readily solved and ignored, but is a tool providing important information about materials and films.