ABSTRACT
The other factors influencing the properties of the real surfaces of oxides are the presence of different lattice defects in the surface layer and its chemical composition, which in many cases may be different from that of the bulk. The most obvious defect is the surface itself with its coordinatively nonsaturated atoms. The presence of the so-called dangling bonds at the surface creates electron energy states, usually named intrinsic states, which are considered to be present even in the case of a pure and strictly stoichiometric surface. On the other hand, the structural defects on the surface or adsorbed impurities create the extrinsic surface states.
