Ultrasonic Modification of Aluminum Surfaces: Comparison between Thermal and Ultrasonic Effects.

Ultrasound has become an increasingly popular tool in the modification of metal surfaces, imbuing them with various desired characteristics and functionalities. The exact role played by ultrasound in such processes remains largely speculative and thus requires clarification. In this study, aluminum was taken as a model metal to probe the nature of the surface modification, focusing on both chemical and physical changes. Using metal plates as substrates, the formation of a characteristic porous surface structure was ascertained to arise from a purely thermal mechanism, with the ultrasound providing an inhibitory influence when compared with controlled experiments matching the thermal conditions of sonication. No beneficial effect was observed through sonication, with regards to surface texture, porosity, and electrochemistry. However, for metal powders, a pronounced change in the phase composition was observed following ultrasonic exposure, largely attributed to the growth of bayerite from the surface. The immobilization of the powder on a thin epoxy film nullified such effects. This suggests that the changes in phase composition are due to the effect of ultrasound-induced mechanical stirring and high speed particle motion on the dissolution and reprecipitation of the metal oxide and hydrated oxide species. This work is of significant value to researchers both in materials science and in sonochemistry

Effect of Surface Functionalization of Metal Wire on Electrophysical Properties of Inductive Elements

The development of the microelectronics industry requires a new element basis with reduced size and increased functionality. The most important components in modern microelectronic integrated circuits are passive elements. One of the key challenges in order to improve the functionality of integrated circuits is to increase the quality of passive elements composing them. In this paper we suggest a novel approach to increase the quality factor Q of inductors by the surface modification and functionalization of the metal components. Ultrasound induced surface modification of metal wires led to the formation of a porous surface structure, which further can be functionalized with magnetite nanoparticles using layer-by-layer assembly technique. The surface modification and deposition of magnetite nanoparticles was investigated with SEM, XRD, and contact angle measurements. Additionally, inductance and resistance measurements, as the main parameters determining the Q-factor of inductors, were carried out. Samples with high number of magnetic nanoparticle–polyelectrolyte bilayers demonstrate a significant increase in inductance and a slight decrease in resistance in comparison to uncoated ones. The combination of these factors led to enhancement the Q-factor of the investigated inductive elements

Real-Time Structural and Optical Study of Growth and Packing Behavior of Perylene Diimide Derivative Thin Films: Influence of Side-Chain Modification

We study the growth of two n-type small-molecule organic semiconductors from the perylene diimide family: <i>N</i>,<i>N</i>′-bis-(2-ethylhexyl)-dicyanoperylene-3,4:9,10-bis­(dicarboximide) (PDIR-CN₂) and <i>N</i>,<i>N</i>′-1<i>H</i>,1<i>H</i>-perfluorobutyl-dicyanoperylene-3,4:9,10-bis­(dicarboximide) (PDIF-CN₂) whose chemical structures differ only in the imide substituents, branched alkyl chains −C₈H₁₆ and linear fluoroalkyl chains −C₄F₇H₂, respectively. Both types of substituents introduce some degree of steric hindrance for intermolecular interactions, affecting solid-state packing during thin film formation, and thus induce specific structure-dependent optoelectronic properties in thin films. The transition from an amorphous structure to crystalline domains with strong intermolecular coupling was followed in situ and in real time during growth. We investigated the structural and morphological properties by X-ray diffraction and atomic force microscopy as a function of the substrate temperature and chemical structure. We examined the relationship between the structural properties and thin film optical signatures probed via differential reflectance spectroscopy, ellipsometry, and temperature-dependent photoluminescence. A new crystalline PDIR-CN₂ polymorph at high temperatures emerges. In addition, we observed in PDIF-CN₂ that the fluorinated chains contribute to crystallization inhibition because of the higher overall steric hindrance compared to the alkyl chains

Growth, Structure, and Anisotropic Optical Properties of Difluoro-anthradithiophene Thin Films

Anthradithiophene (ADT) and its functionalized derivatives have proven to be attractive for high-performance electronic devices based on small-molecule organic semiconductors. In this manuscript we investigate the structural and optical properties of thin films of difluoro-anthradithiophene (diF-ADT), an ADT derivative, grown by organic molecular beam deposition (OMBD). By grazing incidence X-ray diffraction and reciprocal space maps, we show that diF-ADT crystallizes in a thin film structure similar to the single crystal unit cell. In addition, we investigate the growth characteristics with atomic force microscopy (AFM) and show an increase of surface mound sizes with elevated substrate temperature. Optical absorption measurements reveal a clear vibronic progression in both solution and thin film spectra along with a distinct optical anisotropy related to the molecular orientation in thin films

Epitaxial Growth of an Organic p–n Heterojunction: C₆₀ on Single-Crystal Pentacene

Designing molecular p–n heterojunction structures, i.e., electron donor–acceptor contacts, is one of the central challenges for further development of organic electronic devices. In the present study, a well-defined p–n heterojunction of two representative molecular semiconductors, pentacene and C₆₀, formed on the single-crystal surface of pentacene is precisely investigated in terms of its growth behavior and crystallographic structure. C₆₀ assembles into a (111)-oriented face-centered-cubic crystal structure with a specific epitaxial orientation on the (001) surface of the pentacene single crystal. The present experimental findings provide molecular scale insights into the formation mechanisms of the organic p–n heterojunction through an accurate structural analysis of the single-crystalline molecular contact