ABSTRACT
The correlation between the properties of solids and their structure is fundamental for Solid State Physics and Materials Science. This correlation applies to the atomic as well as to the electronic structure. In the past, attention has been focussed primarily on the atomic structure and/or the microstructure of solids in order to vary their properties. In fact, several methods such as melt spinning, implantation, ball milling or cluster-assembling have been developed to synthesize materials with new atomic structures, new microstructures and, hence, new properties. It is the common feature of all materials resulting from these procedures that they are electrically neutral, i.e. their positive and negative electric charges are balanced. The modification of the properties of solids by deviating from charge neutrality has received remarkably little attention so far, although it is well established that the properties (e.g. the optical, magnetic, chemical properties, etc.) of electrically charged clusters deviate significantly from the ones of their electrically neutral counterparts (Henglein, 1979 and 1997). In fact, solids with nanometer-sized microstructures may open the way to generate materials with an excess or a deficit of electrons or holes of up to about 0.3 electrons/holes per atom (Gleiter, 2001). Such deviations from charge neutrality may be achieved either by means of an externally applied voltage or by space charges at interfaces between materials with different chemical compositions (or combinations of both). As many properties of solid materials depend on their electronic structure, significant deviations from
charge neutrality result in materials with new, yet mostly unexplored properties such as modified electric, ferromagnetic, optical, etc. properties as well as alloys of conventionally immiscible components or materials with new types of atomic structures. Existing and conceivable new technological applications of solids deviating from charge neutrality will be discussed.
