Growth of Palladium on Zinc Oxide Surfaces

Abstract

Metal oxide semiconductors, both pure and metal doped, play a key role in many of todays industries and, as such, it is desirable to seek a fuller understanding of the mechanisms governing the many processes in which these compounds are involved. Areas such as catalysis and gas sensing rely heavily on the use of metal oxide semiconductors, and it is the unusual surface properties which these compounds exhibit that allow them to be employed in such areas. Within these fields it has been found for several semiconductors that, through doping the surface of the semiconductor with a reactive metal, the sensitivity and selectivity of the system can be improved to a level greater than that of either of the two components. In order to improve our understanding of the processes occurring at the surface of the metal-semiconductor system, so called ‘model systems’ are employed. These involve the simulation of the real surface through the deposition of measured amounts of metal onto a single crystal surface of the semiconductor under Ultra High Vacuum conditions. In this way, surface sensitive spectroscopic techniques such as XPS, AES and SIMS can be used to examine surfaces prepared under conditions designed to minimise surface defects and contamination. The work described in this poster is an example of such a model system — that of palladium covered zinc oxide.