Amorphous semiconducting nature

The semiconductive nature of some PFSs makes them excellent candidates for applications where some conductivity is needed but high values are not desirable due to the associated effects of magnetic fields. For example, amorphous PFSs such as 73 (R = Me R =Ph) possess appreciable hole mobilities (ca. 10 cm V and appear promising as charge dissipation materials with potential applications as protective... 

The PFC is considered to be amorphous, that is, in case of semiconductive nature of electronic conductivity, it cannot be doped retaining its intrinsic conductivity. 

While considering trends in further investigations, one has to pay special attention to the effect of electroreflection. So far, this effect has been used to obtain information on the structure of the near-the-surface region of a semiconductor, but the electroreflection method makes it possible, in principle, to study electrode reactions, adsorption, and the properties of thin surface layers. Let us note in this respect an important role of objects with semiconducting properties for electrochemistry and photoelectrochemistry as a whole. Here we mean oxide and other films, polylayers of adsorbed organic substances, and other materials on the surface of metallic electrodes. Anomalies in the electrochemical behavior of such systems are frequently explained by their semiconductor nature. Yet, there is a barrier between electrochemistry and photoelectrochemistry of crystalline semiconductors with electronic conductivity, on the one hand, and electrochemistry of oxide films, which usually are amorphous and have appreciable ionic conductivity, on the other hand. To overcome this barrier is the task of further investigations. 

In a sulfuric acid solution, the formation of PbO during the corrosion of lead without any other phase of PbO (1 < x < 2) has been observed the sensitivity of the method approached the monolayer level [742]. Passive films on nickel and iron surfaces have been studied both with polychromatic and monochromatic light [739]. Characteristic data of the semiconducting surface layers (fiatband potentials, charge carrier densities, bandgap energies) could be obtained. The limitations of the traditional band model that is used in solid state physics for ideal crystalline solids with practically unlimited periodicity have been pointed out and the additional difficulties caused by the polycrystalline or even amorphous nature of these films were stressed. 

The fourth volume concentrates mainly on the properties of semiconducting compounds, including transition-metal silicides, amorphous and liquid semiconductors, and particularly the nature of the chemical bonds in these materials. 

The electrical properties of semiconductors depend on the perfection of the crystal structure and the nature of the impurities it contains. However, the decisive factor responsible for semiconductor properties is the short-range order. By this is meant the symmetry of the electron shells, the valence an es, the interatomic distances, etc., i.e., the nature of the forces of the chemical interaction between the atoms. This is indicated by the fact that the semiconducting properties of many crystalline semiconductors are retained after melting [1] and also by the existence of a large number of liquid, amorphous, and glassy semiconductors. 

Many materials exhibit size-dependent properties as system dimensions approach the atomic or molecular level. For example, metal and semiconducting nanoclusters with dimensions of a few nanometers exhibit remarkable optical, electrical, mechanical, catalytic, and magnetic properties (Murray et al 2000). Nanocluster properties differ significantly from corresponding bulk properties they depend on the quantum-level electronic structure of the ensemble and the ratio of surface to bulk atoms, and they provide the foundation for a wide range of innovative nanotechnologies. Unfortunately, much less is known about the properties of amorphous, polymeric materials in nanoscopic structures. Because the characteristic dimensions typically associated with polymeric molecules are on the order of 5- to 10-nm, it is natural to expect size-dependent properties in polymeric structures with dimensions from 10 to 100 nm. 

---