Auger Line Shapes as a Probe of Electronic Structure in Covalent Systems

Our goal has been to develop a generally applicable, semi-empirical approach for quantitatively interpreting Auger line shapes for covalently bonded systems. In this regard we examine four main topics. First, because the Cini-Sawatzky theory was originally derived for initially filled, single bands in metals, we present our grounds for applying it to covalent systems. Second, we examine the problem of unfilled bands, and third, emphasise the importance of satellites. The role of satellites are examined with regard to as benzene, graphite, and the new carbon material, C 60 , often referred to as "buckyball". Finally we present result of an application to "carbidic" carbon on Ni, where fundamental new information was obtained concerning the nucleation of graphite at higher temperatures. In our discussions, results from the interpretation of the C KVV Auger line shapes of five different gas phase hydrocarbons (methane, ethane, cyclohexane, benzene, and ethylene), five different solids (polyethylene, diamond, graphite, "buckyball", and nickel carbides), and a molecularly chemisorbed system (ethylene/Ni) are included.