Electronic properties, layer description

It is important to keep in mind that the chemical behavior of a surface determines the surface electronic properties. Thus, variations, e.g. due to adsorbate atoms, have a significant influence. This aspect will be focused on as the next topic with the description of selected substrate layers which were exposed to different types of gaseous molecules. 

The slab model consists of a film formed by a few atomic layers parallel to the (hkl) crystalline plane of interest. The film, of finite thickness, is limited by two surface planes, possibly related by symmetry. For sufficiently thick slabs, this kind of model can provide a faithful description of the ideal surface. The adequacy of the model must be checked by considering convergence of geometry, energy, and electronic properties with an increasing number of atomic layers included in the slab. 

A proper description of interfacial electronic properties requires going beyond a simple two-molecule representation containing one donor and one acceptor unit [10]. In order to assess the validity of LRC functionals for systems of large size, we have computed the evolution of the HOMOxtf and LUMOtcnq in isolated one-dimensional stacks containing from one to live layers. We compared the coB97X functional, which gave the most reliable results in the previous section, to the BHLYP functional that also... 

MIM or SIM [82-84] diodes to the PPV/A1 interface provides a good qualitative understanding of the device operation in terms of Schottky diodes for high impurity densities (typically 2> 1017 cm-3) and rigid band diodes for low impurity densities (typically<1017 cm-3). Figure 15-14a and b schematically show the two models for the different impurity concentrations. However, these models do not allow a quantitative description of the open circuit voltage or the spectral resolved photocurrent spectrum. The transport properties of single-layer polymer diodes with asymmetric metal electrodes are well described by the double-carrier current flow equation (Eq. (15.4)) where the holes show a field dependent mobility and the electrons of the holes show a temperature-dependent trap distribution. 

Abstract Analytical solution of the associative mean spherical approximation (AMSA) and the modified version of the mean spherical approximation - the mass action law (MSA-MAL) approach for ion and ion-dipole models are used to revise the concept of ion association in the theory of electrolyte solutions. In the considered approach in contrast to the traditional one both free and associated ion electrostatic contributions are taken into account and therefore the revised version of ion association concept is correct for weak and strong regimes of ion association. It is shown that AMSA theory is more preferable for the description of thermodynamic properties while the modified version of the MSA-MAL theory is more useful for the description of electrical properties. The capabilities of the developed approaches are illustrated by the description of thermodynamic and transport properties of electrolyte solutions in weakly polar solvents. The proposed theory is applied to explain the anomalous properties of electrical double layer in a low temperature region and for the treatment of the effect of electrolyte on the rate of intramolecular electron transfer. The revised concept of ion association is also used to describe the concentration dependence of dielectric constant in electrolyte solutions. 

In this chapter some aspects of the present state of the concept of ion association in the theory of electrolyte solutions will be reviewed. For simplification our consideration will be restricted to a symmetrical electrolyte. It will be demonstrated that the concept of ion association is useful not only to describe such properties as osmotic and activity coefficients, electroconductivity and dielectric constant of nonaqueous electrolyte solutions, which traditionally are explained using the ion association ideas, but also for the treatment of electrolyte contributions to the intramolecular electron transfer in weakly polar solvents [21, 22] and for the interpretation of specific anomalous properties of electrical double layer in low temperature region [23, 24], The majority of these properties can be described within the McMillan-Mayer or ion approach when the solvent is considered as a dielectric continuum and only ions are treated explicitly. However, the description of dielectric properties also requires the solvent molecules being explicitly taken into account which can be done at the Born-Oppenheimer or ion-molecular approach. This approach also leads to the correct description of different solvation effects. We should also note that effects of ion association require a different treatment of the thermodynamic and electrical properties. For the thermodynamic properties such as the osmotic and activity coefficients or the adsorption coefficient of electrical double layer, the ion pairs give a direct contribution and these properties are described correctly in the framework of AMSA theory. Since the ion pairs have no free electric charges, they give polarization effects only for such electrical properties as electroconductivity, dielectric constant or capacitance of electrical double layer. Hence, to describe the electrical properties, it is more convenient to modify MSA-MAL approach by including the ion pairs as new polar entities. 

An accurate description of a single-layer LED should be obtained by using the injection and transport properties of electrons and holes, determined independently from the Schottky energy barrier and single-carrier device measurements, to describe the two carrier LED structure. To test this procedure consider structures fabricated from the conjugated oligomer 2-metooxy-5-(2 -etoylhexyloxy)-... 

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