Electronic transport, general description

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)...

The thermodynamics of insertion electrodes is discussed in detail in Chapter 7. In the present chapter attention is focused mainly on the general kinetic aspects of electrode reactions and on the techniques by which the transport of species within electrodes may be determined. The electrodes are treated in a general fashion as exhibiting mixed ionic and electronic transport, and attention is concentrated on the description of the coupled transport of these species. In this context it is useful to consider that an electronically conducting lead provides the electrons at the electrodes and compensates the charges of the ions transferred by the electrolyte. 

Table 4.1-103 Electronic transport in beryllium compounds, general description...

The theory of electron transport through polymer films at the surfaces of electrodes has blossomed under the guidance and development of Saveant and his group, and many others (51-60). Saveant s major contribution was to provide a general, mathematical description of charge transfer during electrocatalytic oxidation or reduction of a substrate in solution. 

A general mathematical formulation and a detailed analysis of the dynamic behavior of this mass-transport induced N-NDR oscillations were given by Koper and Sluyters [8, 65]. The concentration of the electroactive species at the electrode decreases owing to the electron-transfer reaction and increases due to diffusion. For the mathematical description of diffusion, Koper and Sluyters [65] invoke a linear diffusion layer approximation, that is, it is assumed that there is a diffusion layer of constant thickness, and the concentration profile across the diffusion layer adjusts instantaneously to a linear profile. Thus, they arrive at the following dimensionless set of equations for the double layer potential, [Pg.117]

We found earlier that a theoretical consideration of displacement and transport exerts a unifying influence on separation science, bringing diverse methods under a common descriptive umbrella. The theory leads in a natural way to the formation of categories of separations which can be considered the beginning of a fundamental classificatory system. Here we generalize the results of transport theory to develop a fundamental basis for classification. While the resulting scheme will not be a complete polythetic classification, it will be based upon some of the most fundamental features of the separation process. These basic features, incorporated in the classification, should correlate well with other properties of separations in the same way that the number of outer-shell electrons is directly related to the diverse properties of the elements of the periodic table. This transport-oriented... 

In this section, we first consider a general model of the faradaic processes occurring at the semiconductor-electrolyte interface due to Gerischer [11]. From Gerischer s model, using the potential distribution at the interface, we may derive a Tafel-type description of the variation of electron transfer with potential and we will then consider the transport limitations discussed above. We then turn to the case of intermediate interactions, in which the electron transfer process is mediated by surface states on the semiconductor and, finally, we consider situations in which the simple Gerischer model breaks down. 

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