The first fully heterocyclic circulene very recently isolated, C(16)S(8), was studied by means of high accurate methods, allowing reliable predictions and interpretations of the structural and electronic properties of organic molecules bearing sulfur and selenium atoms. The changes induced by the oxidation process and the S/Se substitution on some of its properties and the infrared (IR) spectra were analyzed, allowing a comprehensive assignment of the bands observed in the case of C(16)S(8). The results confirmed the planarity and a large surface area of C(16)S(8), which remain in C(16)S(4)Se(4) and C(16)Se(4) derivatives, favoring their use for H(2) adsorption. The molecules were shown to have a strong aromatic character, while the IR spectrum of C(16)S(8) was elucidated, toward its possible application for a better understanding of the new class of materials; the IR signal associated to the asymmetric stretching of the CC bonds can be used as a structural signature to identify the neutral from the radical forms whose structural planarity was found to resist against the oxidation process. Some of the electronic and physical properties characterizing good electron-donating (ED) and charge-transporting (CT) capacity such as the frontier molecular orbital energies (E(HOMO), E(LUMO)), the ionization potential (IP), and the reorganization energy (lambda(h)/lambda(e) for hole/electron) were calculated and the influence of the cyclic structure of C(16)S(8) on them discussed. C(16)S(8), C(16)S(4)Se(4), and C(16)Se(4) were found to display a comparable/much lower lambda(h) and higher IP and E(LUMO) than those for some of the already well-known field-effect transistors (FET) materials such as pentacene, anthracene, and DT-TTF; further investigation for this issue is strongly recommended.

The size distribution of Pb inclusions formed by high-dose ion implantation in crystalline Si has been studied with a variety of experimental techniques. Results obtained from small angle x-ray scattering, transmission electron microscopy, and low-temperature magnetic moment measurements are compared. For samples implanted at room temperature, the results depend on which technique has been used, due to the amorphization of the silicon. The experiments on the samples implanted at an elevated temperature yield compatible results.

We induced Co to form inclusions in Ag by ion implantation of Co into Ag and by coevaporation of both elements in a MBE system. Mössbauer spectroscopy at 4.2 K reveals the hyperfine fields present in the bulk and at the interface of the precipitates. By post-implanting the 57Co activity into the coevaporated samples, we strongly enhanced this interface population, which facilitates the determination of the associated magnetic hyperfine field. The dependence of the precipitate size on the Co concentration and annealing treatment is monitored. We propose a simple model which allows to estimate the precipitate size in the case of preferential interface population.

In the present study we aim to investigate the onset of Co cluster formation in Ag by Mössbauer spectroscopy. Hyperfine interaction techniques are very powerful in determining the onset of formation of very small clusters because they probe the atomic environment present at the radioactive probe atom's site. We employed different sample preparation techniques and discuss the differences between them. We could establish the proper conditions for obtaining a large fraction of Co dimers. The behaviour of the different components in the Mössbauer spectra as a function of the Co concentration allows us to estimate the typical trapping radius for Co dimer formation.