Electrical effects field effect

In aromatic compounds carbon-13 shifts are largely determined by mesomeric (resonance) and inductive effects. Field effects arising from through-space polarization of the n system by the electric field of a substituent, and the influences of steric (y) effects on the ortho carbon nuclei should also be considered. Substituted carbon (C-l) shifts are further influenced by the anisotropy effect of triple bonds (alkynyl and cyano groups) and by heavy atom shielding. 

Electric charge transport across such interface is less efficient than in the case of homogeneous metal/pentacene interface. This is reflected by more than one order of magnitude lower effective field-effect mobility, observed in the samples fabricated by the growth rate of 0.05 nm/min (Fig. 1(a), bottommost curve). The existence of plateau in mobility vs. thickness curve (Fig. 1(b)) is likely to be a consequence of gradual closing of the uncovered region near the metallic contacts. 

Before starting the thermodynamic analysis of electric-chemical field effects it is necessary to recall some relations familiar from processes in the absence of external electric fields. The most general equilibrium condition for processes where the temperature and the pressure are under experimental control is that the characteristic Gibbs free energy is at its minimum. The Gibbs free energy is defined by... 

The transformed Gibbs free energy clearly decreases in the presence of electric fields. This property is required for a consistent thermodynamic treatment of electric-chemical field effects. 

Figure Bl.22.4. Differential IR absorption spectra from a metal-oxide silicon field-effect transistor (MOSFET) as a fiinction of gate voltage (or inversion layer density, n, which is the parameter reported in the figure). Clear peaks are seen in these spectra for the 0-1, 0-2 and 0-3 inter-electric-field subband transitions that develop for charge carriers when confined to a narrow (<100 A) region near the oxide-semiconductor interface. The inset shows a schematic representation of the attenuated total reflection (ATR) arrangement used in these experiments. These data provide an example of the use of ATR IR spectroscopy for the probing of electronic states in semiconductor surfaces [44]-...

Accuracies achieved by ECG are usually about 0.125 mm, although some claims have been made for accuracies an order of magnitude better. A drawback of ECG is the loss of accuracy when inside corners are ground. Because of the electric field effects, radii better than 0.25—0.375 mm can seldom be achieved. 

Binary Electrolyte Mixtures When electrolytes are added to a solvent, they dissociate to a certain degree. It would appear that the solution contains at least three components solvent, anions, and cations, if the solution is to remain neutral in charge at each point (assuming the absence of any applied electric potential field), the anions and cations diffuse effectively as a single component, as for molecular diffusion. The diffusion or the anionic and cationic species in the solvent can thus be treated as a binary mixture. 

Theory Cross-flow-elecfrofiltration can theoretically be treated as if it were cross-flow filtration with superimposed electrical effects. These electrical effects include elecfroosmosis in the filter medium and cake and elecfrophoresis of the particles in the shiny. The addition of the applied electric field can, nowever, result in some quahta-tive differences in permeate-flux-parameter dependences. 

In a d.c. system the current distribution through the cross-section of a current-canying conductor is uniform as it consists of only the resistance. In an a.c. system the inductive effect caused by the induced-electric field causes skin and proximity effects. These effects play a complex role in determining the current distribution through the cross-section of a conductor. In an a.c. system, the inductance of a conductor varies with the depth of the conductor due to the skin effect. This inductance is further affected by the presence of another current-carrying conductor in the vicinity (the proximity effect). Thus, the impedance and the current distribution (density) through the cross-section of the conductor vaiy. Both these factors on an a.c. system tend to increase the effective... 

Shottky Emission - This is also a thermionic type of emission except that in this case, the applied electric field effectively decreases the work function of the material, and more electrons can then escape. 

Destruction by Electric Field Effects - It has been observed that some organisms are killed in midstream without contaet with the eleetrodes. The organisms were observed to oseillate in phase with the eleetrie field. Hence, mieroorganism kill can also be aseribed to ehanges eaused by ehanging electromotive forees resulting from the impressed AC. 

Neumann, E. Principles of electric field effects in chemical and biological systems, in Topics in Bioelectrochemistry and Bioenergetics, Vol. 4, (ed.) Milazzo, G., New York, Wiley 1981... 

We consider first the polarizability of a molecule consisting of two or more polarizable parts which may be atoms, bonds, or other units. When the molecule is placed in an electric field the effective field which induces dipole moments in various parts is not just the external field but rather the local field which is influenced by the induced dipoles of the other parts. The classical theory of this interaction of polarizable units was presented by Silberstein36 and others and is summarized by Stuart in his monograph.40 The writer has examined the problem in quantum theory and finds that the same results are obtained to the order of approximation being considered. 

Downs et al, Photo- and Electric Field Effects in Energetic Materials, PATR 4711 (1974)... 

G. Pacchioni, J.R. Lomas, and F. Illas, Electric field effects in heterogeneous catalysis, Molecular Catalysis A Chemical 119, 263-273 (1997). 

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