Electronic transport, general

Electronic Transport, General Description. Boron Nitride, Cubic (BNcub). Owing to the large gap, all literature data refer to extrinsic conduction. For the temperature dependence of the conductivity, see Fig. 4.1-58. Hall measurements on nominally undoped thin films yield values of the carrier mobility of around 500cm /V s. 

Electronic Transport, General Description. Aluminium Nitride (AIN). Owing to the large energy gap, transport is always extrinsic. Typical numerical values for the electrical conductivity of undoped single crystals lie in the range 10 cm < cr< 10- f2-lcm-l. 

Electronic Transport, General Description. Gallium Nitride (GaN). Undoped GaN is normally an n-type conductor. Carrier concentrations in undoped films can vary from 5 x 10 cm to 5 x 10 cm because of unintentional incorporation of extrinsic impurities, mainly silicon and oxygen. In the purest a-GaN material (w = 10 cm ), conductivities of the order of... 

Electronic Transport, General Description. Indium Phosphide (InP). The transport properties are determined mainly by the electrons in the Tec minimum. Above 800 K, multivalley conduction, where the Lee minimum is involved, becomes important. 

Electronic Transport, General Description. Magnesium Oxide (MgO). Electrical transport measurements on alkaline earth oxides encounter several difficulties, such as high resistance at low temperatures, a strong influence of surface layers, and high-temperature thermionic emission. The partly contradictory results depend considerably on the purity and nature of the samples (pressed porous powders, sintered samples, polycrystals, and single crystals) and on the experimental conditions. 

Table 4.1-165 Electronic transport, general description Cadmium oxide (CdO)...

Light and photosynthetic electron transport convert DPEs into free radicals of undetermined stmcture. The radicals produced in the presence of the bipyridinium and DPE herbicides decrease leaf chlorophyll and carotenoid content and initiate general destmction of chloroplasts with concomitant formation of short-chain hydrocarbons from polyunsaturated fatty acids (37,97). 

The physical properties of tellurium are generally anistropic. This is so for compressibility, thermal expansion, reflectivity, infrared absorption, and electronic transport. Owing to its weak lateral atomic bonds, crystal imperfections readily occur in single crystals as dislocations and point defects. 

These results may be viewed in the wider context of interactions between potential ligands of multifunctional xenobiotics and metal cations in aquatic environments and the subtle effects of the oxidation level of cations such as Fe. The Fe status of a bacterial culture has an important influence on synthesis of the redox systems of the cell since many of the electron transport proteins contain Fe. This is not generally evaluated systematically, although the degradation of tetrachloromethane by a strain of Pseudomonas sp. under denitrifying conditions clearly illustrated the adverse effect of Fe on the biotransformation of the substrate (Lewis and Crawford 1993 Tatara et al. 1993). This possibility should therefore be taken into account in the application of such organisms to bioremediation programs. 

Several categories of models appear as the basis for the study of molecular electronics in general, and molecular transport junctions in particular. These are the geometrical (or molecular), Hamiltonian, and transport analysis models. 

Molecular transport junctions differ from traditional chemical kinetics in that they are fundamentally electronic rather than nuclear - in chemical kinetics one talks about nucleophilic substitution reactions, isomerization processes, catalytic insertions, crystal forming, lattice changes - nearly always these are describing nuclear motion (although the electronic behavior underlies it). In general the areas of both electron transfer and electron transport focus directly on the charge motion arising from electrons, and are therefore intrinsically quantum mechanical. 

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