Photoelectron spectroscopy of polyconjugated polymer surfaces and interfaces

Polymers as electronic materials are finding ever increasing use in the electronics industry. The study of the electronic and chemical structure of polymer surfaces and interfaces has received relatively little attention, however, compared with the surfaces of metals and inorganic semiconductors. The most interesting polymer materials today, from a point of view of electronic properties and future applications, are the polyconjugated polymers, which can be doped to a state of very high electrical conductivity, so-called 'conducting polymers', or merely conjugated polymers. The connection between the chemical (geometrical) and electronic structure of polyconjugated polymers, as well as the relation to surface structure, is discussed in comparison with the surfaces of inorganic semiconductors. It is shown that for well prepared samples, the surface electronic structure of certain ideal polymer materials can be equal to that in the bulk. In the initial stages of metal-polymer interface formation, however, certain electronic and chemical structural changes can occur. Two examples are discussed in detail: changes in the electronic structure observed at the surface of a (poly)conjugated polymer (i) upon doping, and (ii) upon the initial stages of metallization.