Electronic field effect

Reactivities of lithium pinacolone enolate with various ketones were determined by competition experiments in diethyl ether at —78 °C. For a series of substrates, MeCOCH2X and PhCOCH2X, pi(X) = 6.62 and 7.61, indicating a large electronic field effect. ... 

Originality The synthesis of polyfluorenes having lateral high electron field-effect... 

Empolying such a Ca passivated Si02 insulator in combination with Ca drain-source electrodes, n-t5q3c pentacene OFETs can be realised as has been demonstrated by Ahles et al. [29]. This, however, holds only for thin Ca layers as will be shown in the following, where the influence of the Ca passivation thickness on the electron transport in pentacene OFETs is discussed. Illustrated in Figiue 24.8 is the electron field effect mobility in dependence of the Ca thickness. By eonsidering the mobility of pristine devices, which have not... 

The effect of bulk of the substituents on the activity of the compounds is probably marginal. The authors [78] suggest that the electronic field effect seems to be a highly important factor in determining the compounds activity in vitro and in vivo. 

The observed reduction in electron field-effect mobility was then used as an indicator of when the phase segregation process illustrated in Figure 8.8c was taking place. Single OFETs were annealed under high vacuum at temperatures of 130 and 160 °C, and the field-effect mobilities of holes and electrons were measured. The resulting data are plotted in Figure 8.13. Since in this case the measurements are made while at elevated temperatures, the effects of temperature-dependent transport [51, 88] had also to be considered. 

To relate the measured electron field-effect mobility to the concentration of fuller-ene molecules at the semiconductor-dielectric interface, an implementation of percolation theory was employed [106]. Details of the derivation are given elsewhere [101], but it was found that the following equation gave an adequate description of the relationship (when fullerene aggregation is neglected) ... 

Here jUe is the electron field-effect mobility, c is the fullerene site occupation probability (c = Cl Co), p is the bond occupation probability, pc is the threshold bond occupation probability for percolation, a is the wavefunction overlap parameter of the fullerene molecules, and a is given by the following function ... 

By converting the measured electron field-effect mobilities in Figure 8.17a into concentrations using Eq. (8.6), the solution to the diffusion equation (Eq. (8.5)) could be fitted to the data and an approximate diffusion coefficient of D = 5 nm s could be extracted for [60JPCBM in P3HTat a temperature of 130 °C. 

The structure-activity relationships between toxicity (log BR), monitored as cell population growth of Tetrahymena pyriformis and a number of molecular descriptors including the log 1-octanol/water partition coefficient (log Kqw). the electronic field effect (F), and the ability to donate hydrogen (Hd) have been examined for a series of para-substituted phenols. The equation log BR = 0.6849 (log Kq ) + 0.9439 (F) + 0.3373 (Hd) -1.3764, n = 29 has been found to be a good model for these derivatives and explains 91.1% of toxicity variability. Four derivatives, however, were found to lie outside the 95% confidence interval. The nitro, amino, and azophenyl derivatives were more toxic than predicted and the carboxyl derivative was less toxic than predicted. 

Fig. 14 Electron field-effect mobility and threshold voltage in dependence on the Ca interlayer thickness. The inset shows the layout of the measured devices. The values have been obtained for devices unexposed to thermal or electrical stress. A cyclic electrical stress leads to an improvement of the device characteristics with a maximal electron field-effect mobility of 0.17cm s and...

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