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This paper presents the results of the investigation of the effect of pH of highly acidic medium (pH 0 and 1) on the structure of the electronic spectra of polyaniline films in the spectral range 300–900 nm. The analysis was carried out using the Alentsev–Fock method, which requires no preliminarily notion about the possible shape and/or number of the individual absorption bands and extensive statistical calculations. Along with the six absorption maximums described earlier by other authors three new individual bands were separated. On the basis of the comparison of our results with the literature data, we are inclined to assign the new band near 530–570 nm (depending on the pH) to the donor–acceptor interaction between the quinoid fragments and the counter anions and the new band at λmax>900 nm to the ‘free carriers’ absorption. We also suppose that the new band near 810–830 nm may be associated with the second absorption band of the cation-radical dimers. The effect of an increase in pH on the structure of polyaniline absorption spectra manifests itself in the increase of the portions of the bands corresponding to different electron transitions in the quinoid fragments, as well as in the decrease of the portions of the bands related to the conductivity of the film (i.e. the bands of the cation-radical dimers (or polarons) and free charge carriers).

This paper reviews recent work on electrochromic W-oxide-based films and devices Computed data an presented for electronic structure and optical properties of crystalline WO3. Techniques for mak ...

This paper reviews thermodynamic, spectroscopic and X-ray diffraction studies of SO 4 2− , Cl − , Br − and I − adsorption at the Au(111) electrode surface. The thermodynamic experiments provided information about surface concentrations of specifically adsorbed anions, Gibbs energies of adsorption and the numbers of unit charge flowing to the interface per one adsorbed anion. Second harmonic generation and surface X-ray scattering revealed the affect of ionic adsorption on the electronic and crystallographic structure of the interface. The atomistic information derived from these microscopic studies was used to discuss the thermodynamic data and to verify the theoretical models of the interface. It has been shown that complete description of ionic adsorption at metal electrodes requires a concerted use of the macroscopic and microscopic techniques.

On the basis of the ab-initio Full-Potential Linearized Augmented Plane Wave method we calculated the electronic structure for a nine layer Ag slab covered by a Cl layer on the top and bottom of the slab. The geometrical arrangement corresponds to a simple overlayer model of the Ag(001) surface and a c(2×2)-Cl adsorbate. For comparison, also the clean Ag(001) slab and the free Cl monolayers were calculated with the same geometry. The distance of the Cl layer from the Ag surface layer was obtained by total energy minimization. The derived Ag-Cl bond length of 2.59 A agrees well with recent experimental results. For the work function a value of 5.9 eV was calculated. The main goal of our paper is the study of surface states, which for the clean Ag(001) surface occur for k-point X at approximately 3 eV above E F (state A of s-like character), and close to E F (state B of p-like character). Upon adsorption of Cl, state B splits into two states, whereby one of them does not interact with the Cl adsorbate and therefore remains approximately at the same energetic position as for the clean Ag(001) surface. The second one interacts in a strongly bonding way and is found 4.25 eV below E F still retaining the p-character at the Ag surface atoms. The fate of state A is not so clear. Although for the Cl covered Ag surface we still find a state near 3 eV, its charge character is quite different from the original state A. There is a second state at 4.3 eV above E F , which still shows the s-like character of state A, but is less localized in the Ag surface layer due to the antibonding interaction with Cl

The aim of the paper is to review certain aspects of the electronic structure and properties of metal—a-semiconductor barriers which are of relevance to the theme of this Conference. The discussion will be confined to amorphous silicon (a-Si) prepared by the plasma decomposition of silane, which is of much current interest as an electronically controllable model material. A brief survey of preparation and of some electronic properties of a-Si will be given. We then turn to the model of an ideal Schottky barrier and discuss its application to metal—a-Si contacts where the localised state distribution in the a-semiconductor has a important effect on barrier space charge and profile. In a more realistic model interfacial states at a thin oxide—semiconductor interface are taken into account. In this connection we shall discuss recent experimental work using internal photoemission to investigate the height of metal/a-Si barriers as a function of the metal workfunction. Analysis of these and other results suggests that interfacial state densities on a-Si barriers lie between 10 13 and 10 14 cm −2 eV −1 , remarkably similar to corresponding values for crystalline Si barriers. The final section of the paper deals with the electronic structure of a-Si p + -i-n + junctions. The promising photovoltaic properties of these devices will briefly be considered.