Atomic Structure of Surfaces with Adsorbates

Abstract

In studies of clean surfaces, the presence of any foreign species is absolutely undesirable. However, a large number of investigations concern surfaces on which a controlled amount of certain foreign atoms or molecules are intentionally added. The foreign species can be added to the surface in different ways, including condensation from vapor phase (adsorption), segregation from the sample bulk, or diffusion along the surface. Taking into account that adsorption is the most widely used technique, the added species is conventionally called the adsorbate. The material of the host surface is called the substrate. In the present chapter, the atomic structure of clean surfaces with adsorbates is discussed. The consideration is limited to adsorbate layers with an effective coverage of up to one atomic layer. Thus, multilayer thin films are beyond the scope of the chapter. Already formed (in most cases, equilibrium) structures are treated, while the dynamic processes involved in their formation will be discussed elsewhere.