Showing papers by "Slawomir Braun published in 2009"
TL;DR: A review of recent work on modeling of organic/metal and organic/organic interfaces can be found in this article, where the strength of the interaction at the interface has been used as the main factor.
Abstract: In this Review, we summarize recent work on modeling of organic/metal and organic/organic interfaces. Some of the models discussed have a semiempirical approach, that is, experimentally derived values are used in combination with theory, and others rely completely of calculations. The models are categorized according to the types of interfaces they apply to, and the strength of the interaction at the interface has been used as the main factor. We explain the basics of the models, their use, and give examples on how the models correlate with experimental results. We stress that given the complexity of organic/metal and organic/organic interface formation, it is crucial to know the exact way in which the interface was formed before choosing the model that is applicable, as none of the models presented covers the whole range of interface interaction strengths (weak physisorption to strong chemisorption).
1,436 citations
TL;DR: In this article, a single-phase cubic cubic (Ti,Si)N solid solutions with a dense columnar microstructure was investigated by analytical transmission electron microscopy, x-ray diffraction, xray photoelectron spectroscopy, and nanoindentation.
Abstract: (Ti1-xSix)Ny (0 ≤ x ≤ 0.20; 0.99 ≤ y(x) ≤ 1.13) thin films deposited by arc evaporation have been investigated by analytical transmission electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, and nanoindentation. Films with x ≤ 0.09 are single-phase cubic (Ti,Si)N solid solutions with a dense columnar microstructure. Films with x > 0.09 have a featherlike microstructure consisting of cubic TiN:Si nanocrystallite bundles separated by metastable SiNz with coherent-to-semicoherent interfaces and a dislocation density of as much as 1014 cm−2 is present. The films exhibit retained composition and hardness between 31 and 42 GPa in annealing experiments to 1000 °C due to segregation of SiNz to the grain boundaries. During annealing at 1100–1200 °C, this tissue phase thickens and transforms to amorphous SiNz. At the same time, Si and N diffuse out of the films via the grain boundaries and TiN recrystallize.
58 citations
TL;DR: In this paper, the frontier energy levels and dipole moment of a series of diarylethene compounds have been calculated using density functional theory and a good agreement is found between the calculated electronic structure and the measured ultraviolet photoelectron spectra.
Abstract: Diarylethene molecules are photochromics (PCs) currently investigated for use in optical write/electrical read memory applications. The impact of the photoisomerization of PCs on the device behavior is analyzed with charge transport models. These results indicate that good electrical current switching can be achieved in a device when the PCs are combined with an organic semiconductor (in multilayered structures or blends). The frontier energy levels and dipole moment of a series of diarylethene compounds have been calculated using density functional theory. A good agreement is found between the calculated electronic structure and the measured ultraviolet photoelectron spectra. Shirts in the frontier energy levels and dipole moment are generated through two different approaches for chemical modification: (i) by changing the chemical nature of the aryl rings or (ii) by adding substituents on the ethylene, bridge. The frontier energy levels can be tuned by more than 2 eV via such chemical modifications. We find that, for this family of photochromic compounds, the photoinduced current switch effect in diodes is mainly due to the modulation in the frontier energy levels rather than the changes in the amplitude of the dipole moment.
42 citations
TL;DR: In this article, the authors demonstrate that by modifying gold substrates with a monolayer of fullerene, a significant decrease in the hole-injection barrier into pentacene films can be achieved.
Abstract: Fine-tuning charge injection barriers between organic materials and electrodes is critical to optimize organic electronic device performance. Here we demonstrate that by modifying gold substrates with a monolayer of fullerene, significant decrease in the hole-injection barrier into pentacene films can be achieved. The insertion of the fullerene monolayer modifies the interfacial dipole and produces an interface where the pentacene molecules form a standing-up orientation with their long axis parallel to the surface normal. The latter effect lowers the vertical ionization energy of the pentacene molecules at the interface as compared to the pentacene-on-Au case, as well as improves the pi-pi overlap between the pentacene molecules that will likely enhance the transport properties in corresponding devices.
20 citations