Radiation physics and chemistry of surfaces

Solid mineral surfaces generally present specific vibrational, electronic and atomic properties due to the loss of the bulk symmetry. Under certain circumstances, atomic reconstruction processes can occur. In polymers, the nature of the bonding and the long range organization of the macromolecules make it difficult to define the surface structure, although the recent developments of scanning tunnelling and atomic force microscopy enable one to visualize the surface arrangement. However, when irradiated with an ionizing radiation, the surface layer can be greatly modified, so as to produce a material completely different from the irradiated bulk, as a consequence of bond breaking, chain scissions and the ability to desorb atoms or molecules. The result is a radiation rebuilt surface whose electronic and atomic structures are quite specific, depending on the nature of the radiation and the deposited dose, and leading to original electrical or optical properties. This also enhances the chemical reactivity of the surface, which favours the formation of various interfaces: metal-polymer, polymer-polymer, etc. On the other hand, this radiation fragility must be taken into account in the course of surface analysis using ionizing radiation such as X-rays or energetic light ions.