Chapter 3 - Nature of a Surface

Abstract

A surface is characterized by various specific physical, mechanical, and chemical properties. The surface structure can be crystalline, amorphous, or of a mixed type and very different from the bulk. Depending on material and treatment, the surface can be an insulator, a semiconductor, or a conductor. Technically produced surfaces are flat or curved. A distinction is made among flatness, waviness, and roughness. For the investigation of surface structures, electron-diffraction techniques such as LEED and HEED are mainly used. Surface relaxation can give rise to a multitude of surface structures, depending on the electronic structure of a given material. These displacement reactions are called surface reconstructions. The surfaces of many metal, semiconductor, and compound materials have atomic structures that are different from those expected from the projection of the X-ray bulk unit cell. The energy released by the creation of a surface can also induce chemical changes. In considering the possible surface compositions, single and multicomponent materials should be distinguished. The surface composition of clean plastics is generally homogeneous. Surfaces produced by injection molding may be covered with mold-release agents or other processing impurities that are hard to remove.