Ultra-low-energy ion-beam-synthesis of Ge nanocrystals in thin ALD Al2O3 layers for memory applications

Structural and electrical properties of ALD-grown 5 and 7 nm-thick Al₂O₃ layers before and after implantation of Ge ions (1 keV, 0.5–1 × 10¹⁶ cm^?2) and thermal annealing at temperatures in the 700–1050 °C range are reported. Transmission Electron Microscopy reveals the development of a 1 nm-thick SiO₂-rich layer at the Al₂O₃/Si substrate interface as well as the formation of Ge nanocrystals with a mean diameter of ～5 nm inside the implanted Al₂O₃ layers after annealing at 800 °C for 20 min. Electrical measurements performed on metal–insulator–semiconductor capacitors using Ge-implanted and annealed Al₂O₃ layers reveal charge storage at low-electric fields mainly due to location of the Ge nanocrystals at a tunnelling distance from the substrate and their spatial dispersion inside the Al₂O₃ layers.     

Catalytically Doped Semiconductors for Chemical Gas Sensing: Aerogel‐Like Aluminum‐Containing Zinc Oxide Materials Prepared in the Gas Phase

Atmospheric contamination with organic compounds is undesired in industry and in society because of odor nuisance or potential toxicity. Resistive gas sensors made of semiconducting metal oxides are effective in the detection of gases even at low concentration. Major drawbacks are low selectivity and missing sensitivity toward a targeted compound. Acetaldehyde is selected due to its high relevance in chemical industry and its toxic character. Considering the similarity between gas‐sensing and heterogeneous catalysis (surface reactions, activity, selectivity), it is tempting to transfer concepts. A question of importance is how doping and the resulting change in electronic properties of a metal‐oxide support with semiconducting properties alters reactivity of the surfaces and the functionality in gas‐sensing and in heterogeneous catalysis. A gas‐phase synthesis method is employed for aerogel‐like zinc oxide materials with a defined content of aluminum (n‐doping), which were then used for the assembly of gas sensors. It is shown that only Al‐doped ZnO represents an effective sensor material that is sensitive down to very low concentrations (<350 ppb). The advance in properties relates to a catalytic effect for the doped semiconductor nanomaterial.     

Silicon Nitride Derived from an Organometallic Polymeric Precursor: Preparation and Characterization

Partially crystalline Si₃N₄, with nanosized crystals and a specific surface area greater than 200 m²/g, is obtained by pyrolysis of a commercially available vinylic polysilane in a stream of anhydrous NH₃ to 1000°C. This polymer does not contain N initially. Crystallization to high-purity α-Si₃N₄ proceeds with additional heating above 1400°C under N₂. The changes in crystallinity, powder morphology, infrared spectra, and elemental compositions, for samples annealed from 1000° to 1600°C under N₂, are consistent with an amorphous-to-crystalline transformation. Although macroscopic consolidation and local densification occur at 1400°C, volatilization and accompanying weight loss limit bulk densification. The effect of temperature on specific surface area is examined and related to the sintering process. These results are applicable to pyrolysis, decomposition, and crystallization studies of ceramics synthesized by polymeric precursor routes.     

Zur Beständigkeit beschichteter Holzspanwerkstoffe

Materials, based on, wood particles, such as particleboards and moulded wood particle materials, are mainly used in a coated state for building purposes. In our laboratories investigations have been carried out to determine the service life of these composite materials, by means of accelerated weathering method. For this purpose, different liquid or solid-coated materials were used. The tests aimed at comparing open-air weathering with a short-term weathering test, which has been developed in our laboratory, based on the so-called Xenotest method. Among the liquid coatings, those lacquers based on pigmented polyurethanes turned out to be superior to all other competing systems. Solid coatings, made of pure melamine-formaldehyde resins showed to be very resistant against weathering. 48 to 60 weeks exposure in a Xenotest weathering apparatus seem to be sufficient to simulate 10 years of open-air exposure not only for uncoated but also for coated wood particle materials.     

Measurement of acousto-optic interaction in Germanium in the far infrared

Acousto-optic interaction in a Germanium Bragg cell, which was operated as acoustic resonator, was measured at 119 μm relative to 10.6 μm. The figure of merit of the material was found to be approximately 20% higher in the far infrared. The performance of various acousto-optic materials in the far infrared is briefly discussed.     

Verfahren zur Erstellung auswertbarer Bildvorlagen für mikrovisioplastische Untersuchungen

The mechanical properties of polycristalline materials are depent on the type, the combination and the orientation of the elements in the micro structure. By means of the method of Visioplasticity assumptions are currently realized to analyse kinematic parameters inside of single grains and grain groups. Strength of the free surface of the specimen will be rough by its plastical deformation, it was difficult to register the increments of deformation of the grid. By further development of a method of picture analysis it is also possible to reproduce a 3d-surface by utilization of single light microscopical pictures.     

Substituierte Alkinyle als axiale Liganden an häminähnlich gebundenem Eisen(III) - Einordnung in eine spektrochemische Serie

Substituted Alkinyles as Axial Ligands at Hemine Like Bound Iron(III) - Incorporation into a Spectrochemical Series . Substituted lithium alkynyles Li CC R (R = ^tBu, Ph, p-Cl C₆H₄, Me₃Si, ⁱPr₃Si, Ph₃Si) react with the hemine like macrocyclic iron(III) complex 6,13-di(ethoxycarbonyl)-5, 14-dimethyl-1, 4, 8, 11-tetraazatetradeca-4,6,12,14-tetraenato[2⁻]iron(III)-iodide (formula 2 ;) in tetrahydrofuran to form anionic low-spin di-adducts [fe(CC R)₂]⁻. The incorporation of the alkynyles into a spectrochemical series of the axial ligands (studied by the sharp equatorial-ligand-to-metal CT absorption band) results in the wavelength-sequence (nm): OH⁻ (≈︁ 510) « N₃⁻ (≈︁ 625) < ^tBu CC⁻ (664) < NH₃ (666) < Ph CC⁻ (692) < Ph NH₂ (695) < Me₃Si CC⁻ (698) < SCN⁻ (713) < Ph₃Si C  C⁻ (716) < CN⁻ (739) < 4-picoline (759) < pyridine (765) < nicotinamide (776) < methylnicotinat (788) < pyrazine (798) and points to a significant π-acceptor ability of the silyl substituents.     

Impact of neurite alignment on organelle motion

Intracellular transport is pivotal for cell growth and survival. Malfunctions in this process have been associated with devastating neurodegenerative diseases, highlighting the need for a deeper understanding of the mechanisms involved. Here, we use an experimental methodology that leads neurites of differentiated PC12 cells into either one of two configurations: a one-dimensional configuration, where the neurites align along lines, or a two-dimensional configuration, where the neurites adopt a random orientation and shape on a flat substrate. We subsequently monitored the motion of functional organelles, the lysosomes, inside the neurites. Implementing a time-resolved analysis of the mean-squared displacement, we quantitatively characterized distinct motion modes of the lysosomes. Our results indicate that neurite alignment gives rise to faster diffusive and super-diffusive lysosomal motion than the situation in which the neurites are randomly oriented. After inducing lysosome swelling through an osmotic challenge by sucrose, we confirmed the predicted slowdown in diffusive mobility. Surprisingly, we found that the swelling-induced mobility change affected each of the (sub-/super-)diffusive motion modes differently and depended on the alignment configuration of the neurites. Our findings imply that intracellular transport is significantly and robustly dependent on cell morphology, which might in part be controlled by the extracellular matrix.