Semiconductor/semiconductivity crystalline

Intense research has in recent years been devoted to noncrystalline materials. It was discovered also that the majority of semiconducting boron-rich borides display several properties that resemble those of the noncrystalline solids. Among the amorphous properties are the temperature and field dependencies of electrical conductivity at low temperature, the temperature dependence of thermal conductivity at high temperatures, and the temperature dependence of the magnetic susceptibility. In addition, the boron-rich semiconductors display crystalline properties, for example, the temperature dependence of the thermal condnctivity at low temperatures, the lattice absorption spectra and the possibility to change... 

Various inorganic semiconductors (p-type and/or n-type nonoxide semiconducting materials) sucb as amorphous or crystalline silicon (a-Si or c-Si), gallium arsenide (GaAs), cadmium telluride (CdTe), gallium phosphide (GaP), indium phosphide (InP), copper... 

It should be mentioned that, of the other first-row transition metal oxides crystallizing with the NaCl structure, none has been found to superconduct down to 2.5 K. Some of these oxides undergo magnetic ordering at low temperature and most behave as semiconductors at all temperatures. These would include MnO, FeO, CoO, and NiO. Studies performed on CuO, which has a different crystalline structure, showed only semiconducting behavior to very low temperatures (1.9 K). 

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. 

The mobility and resistivity data of single crystalline zinc oxide samples (measured at room temperature) from different authors, which were reported from 1957 to 2005, are displayed in Fig. 2.6 as a function of the carrier concentration (part of these data were taken from [67]). Undoped ZnO crystals exhibit carrier concentrations as low as 1015 cm-3, while indium-doped crystals reach carrier concentrations up to 7 x 1019cm-3. The mobility data show a large scattering between carrier concentrations of 1017 to 5 x 1018cm-3. This is caused by the fact that zinc oxide is a compound semiconductor that is not as well developed as other semiconducting compounds. For instance, only... 

The elements that fall into this category are silicon, germanium, selenium and tellurium. Iodine shows some semiconducting properties, and phosphorus, sulfur and arsenic can each be obtained in a crystalline form that has the properties of a semiconductor, although this is not the most stable form of these elements under normal conditions. 

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