1. General

Any isolated solid material is necessarily bounded by a surface due to its finite volume. Unlike the mathematical notion of a surface, which corresponds to a strictly two-dimensional space, the physical description of a material's surface is concerned with a transition zone consisting of a few atomic layers at the boundary between the core of the material and a vacuum, a gaseous atmosphere or another dense solid or liquid material. The surface of a material must therefore be considered as a quasi-two-dimensional medium with a very limited spatial extension in the normal direction. The terms surface and interface are often associated, but the latter is usually used in the case of the boundary between a solid material and another dense medium.

Understanding the diverse properties of surfaces requires knowledge of their structure, i.e. the ordered or non-ordered arrangement...