Dielectric roughness

Steudel, S. et al.. Influence of the dielectric roughness on the performance of pentacene transistors, Appl. Phys. Lett. 85, 4400-4402, 2004. 

Fritz, S., Kelley, T., and Frisbie, C., Effect of dielectric roughness on performance of pentacene TFTs and restoration of performance with a polymeric smoothing layer, J. Phys. Chem. B. 109, 10574-10577, 2005. 

Ruiz, R., Choudhary, D., Nickel, B. et al., Pentacene thin film growth, Chem. Mater. 16, 4497, 2004 Laquindanum, J.G., Katz, H. E., Dodabalapur, A., and Lovinger, A. J., -Channel organic transistor materials based on naphthalene frameworks, J. Am. Chem. Soc. 118, 11331, 1996 Fritz, S.E., Kelley, T.W., and Erisbie, C.D., Effect of dielectric roughness on performance of pentacene TFTs and restoration of performance with a polymeric smoothing layer, J. Phys. Chem. B 109,10574, 2005 Nickel,... 

Electrical Insulation. The substitution of a gas for part of a soHd polymer usuaUy results in large changes in the electrical properties of the resulting material. The dielectric constant, dissipation factor, and dielectric strength are aU generaUy lowered in amounts roughly proportional to the amount of gas in the foam. 

Although beryllium oxide [1304-56-9] is in many ways superior to most commonly used alumina-based ceramics, the principal drawback of beryUia-based ceramics is their toxicity thus they should be handled with care. The thermal conductivity of beryUia is roughly about 10 times that of commonly used alumina-based materials (5). BeryUia [1304-56-9] has a lower dielectric constant, a lower coefficient of thermal expansion, and slightly less strength than alumina. Aluminum nitride materials have begun to appear as alternatives to beryUia. Aluminum nitride [24304-00-5] has a thermal conductivity comparable to that of beryUia, but deteriorates less with temperature the thermal conductivity of aluminum nitride can, theoreticaUy, be raised to over 300 W/(m-K) (6). The dielectric constant of aluminum nitride is comparable to that of alumina, but the coefficient of thermal expansion is lower. 

The conductivity of solid dielectrics is roughly independent of temperature below about 20°C but increases according to an Arrhenius function at higher temperatures as processes with different activation energies dominate [ 133 ]. In the case of liquids, the conductivity continues to fall at temperatures less than 20°C and at low ambient temperatures the conductivity is only a fraction of the value measured in the laboratory (3-5.5). The conductivity of liquids can decrease by orders of magnitude if they solidify (5-2.5.5). 

Hence if a laboratory measurement at 25°C yields a conductivity of 100 pS/m the same liquid at -10°C will have a conductivity of about 30 pS/m. The effects of low temperature combined with the elevated dielectric constants of many nonconductive chemicals support use of the 100 pS/m demarcation for nonconductive liquids (5-2.5) rather than the 50 pS/m demarcation used since the 1950s by the petroleum industry. For most hydrocarbons used as fuels, the dielectric constant is roughly 2 and a demarcation of 50 pS/m is adequate, provided the conductivity is determined at the lowest probable handling temperature. 

Most organic reactions are done in solution, and it is therefore important to recognize some of the ways in which solvent can affect the course and rates of reactions. Some of the more common solvents can be roughly classified as in Table 4.10 on the basis of their structure and dielectric constant. There are important differences between protic solvents—solvents fliat contain relatively mobile protons such as those bonded to oxygen, nitrogen, or sulfur—and aprotic solvents, in which all hydrogens are bound to carbon. Similarly, polar solvents, those fliat have high dielectric constants, have effects on reaction rates that are different from those of nonpolar solvent media. 

The Self-Consistent Reaction Field (SCRF) model considers the solvent as a uniform polarizable medium with a dielectric constant of s, with the solute M placed in a suitable shaped hole in the medium. Creation of a cavity in the medium costs energy, i.e. this is a destabilization, while dispersion interactions between the solvent and solute add a stabilization (this is roughly the van der Waals energy between solvent and solute). The electric charge distribution of M will furthermore polarize the medium (induce charge moments), which in turn acts back on the molecule, thereby producing an electrostatic stabilization. The solvation (free) energy may thus be written as... 

Until one develops a feel for recrystallization, the best procedure for known compounds is to duplicate a selection in the literature. For new compounds, a literature citation of a solvent for an analogous structure is often a good beginning point. To assist in the search, Table A3.4 lists several of the common recrystallizing solvents with useful data. The dielectric constant can be taken to be a rough measure of solvent polarity. 

Although the LD model is clearly a rough approximation, it seems to capture the main physics of polar solvents. This model overcomes the key problems associated with the macroscopic model of eq. (2.18), eliminating the dependence of the results on an ill-defined cavity radius and the need to use a dielectric constant which is not defined properly at a short distance from the solute. The LD model provides an effective estimate of solvation energies of the ionic states and allows one to explore the energetics of chemical reactions in polar solvents. 

Then a very thin barrier layer and a copper seed layer are formed (Figs. 21 (b) and 21 (c)>). In order to conduct the electric current, good conductive material, e.g., copper, will be coated on the surface of the copper seed layer which forms a rough surface as shown in Fig. 21(d). Since multilayer s introduction into IC production, the surface coated with copper must be very smooth, clean, and bare of dielectric stacks... 

FIG. 18 Roughness function in dependence of the dimensionless parameters Kih and K2h. The dielectric constants have been taken as gj = 80, 62 = 10. The ratio of the geometrical area to that of the flat surface was taken as 1.62 [37]. 

To begin with, molecular solvents with high permittivities will be considered. Classification of solvents on the basis of their permittivities agrees roughly with classification as polar and non-polar, and the borderline between these two categories is usually considered to be a relative dielectric constant of 30-40. Below this value ion pairs are markedly formed. From... 

The extent of the ionization produced by a Lewis acid is dependent on the nature of the more inert solvent component as well as on the Lewis acid. A trityl bromide-stannic bromide complex of one to one stoichiometry exists in the form of orange-red crystals, obviously ionic. But as is. always the case with crystalline substances, lattice energy is a very important factor in determining the stability and no quantitative predictions can be made about the behaviour of the same substance in solution. Thus the trityl bromide-stannic bromide system dilute in benzene solution seems to consist largely of free trityl bromide, free stannic bromide, and only a small amount of ion pairs.187 There is not even any very considerable fraction of covalent tfityl bromide-stannic bromide complex in solution. The extent of ion pair and ion formation roughly parallels the dielectric constant of the solvents used (Table V). The more polar solvent either provides a... 

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