Why does it take so long to get state aid approved by Brussels?

The European Commission is responsible for ensuring governments comply with the EU’s state aid rules. But are these rules applied fairly across all member states? Ruud van Druenen and Pieter Zwaan present an analysis of the time it takes for the Commission to process state aid cases. They find that although the duration of cases varies substantially, this variation is best explained by characteristics of the state aid measures themselves. They find no evidence that the Commission favours some member states over others when processing cases

CFD analysis of an exceptional cyclist sprint position

A few riders have adopted a rather exceptional and more aerodynamic sprint position where the torso is held low and nearly horizontal and close to the handle bar to reduce the frontal area. The question arises how much aerodynamic benefit can be gained by such a position. This paper presents an aerodynamic analysis of both the regular and the low sprint position in comparison to three more common cycling positions. Computational fluid dynamics simulations are performed with the 3D RANS simulations and the transition SST k–ω model, validated with wind-tunnel measurements. The results are analyzed in terms of frontal area, drag coefficient, drag area, air speed and static pressure distribution, and static pressure coefficient and skin friction coefficient on the cyclist surfaces. It is shown that the drag area for the low sprint position is 24% lower than for the regular position, which renders the former 15% faster than the latter. This 24% improvement is not only the result of the 19% reduction in frontal area, but also caused by a reduction of 7% in drag coefficient due to the changed body position and the related changes in pressure distribution. Evidently, specific training is required to exert large power in the low sprint position.</p

Functionalisation and characterisation of bulk and two-dimensional semiconductors

The continual scaling of semiconductor devices has created a high demand for new techniques and materials that allow the advancement Moore’s Law: the number of transistors on a chip doubles every 12-18 months. The move from planar to three-dimensional (3D) transistor geometries requires compatible doping technologies that meet the demands of Moore’s Law. Monolayer doping (MLD) has shown promise in achieving uniformly doped regions compared to currently implemented techniques. However, the continuous use of silicon (Si) as a device material to satisfy Moore’s law is becoming challenging and new materials are currently being investigated to potentially replace Si. One of these materials is black phosphorus (BP) which displays a high carrier mobility making it a viable candidate for some electronic devices, although the ambient stability of BP is a key challenge, which makes its processing difficult and functionalisation has been employed as a potential protection strategy to enhance its oxidation resistance. Additionally, antimonene (AM) has been proposed as a device material that displays a superior ambient stability compared to BP. This thesis aims to address some of the challenges faced when preparing three materials, Si, BP and AM, for device applications in order to satisfy Moore’s Law. Functionalisation of SiO2 surfaces was used for monolayer doping which resulted in tuning of the electrical properties of Si. The functionalisation of BP was used to enhance its ambient stability while the liquid exfoliation of AM was also investigated

Functionalization of SiO2 surfaces for Si monolayer doping with minimal carbon contamination

Monolayer doping (MLD) involves the functionalization of semiconductor surfaces followed by an annealing step to diffuse the dopant into the substrate. We report an alternative doping method, oxide-MLD, where ultrathin SiO2 overlayers are functionalized with phosphonic acids for doping Si. Similar peak carrier concentrations were achieved when compared with hydrosilylated surfaces (∼2 × 1020 atoms/cm3). Oxide-MLD offers several advantages over conventional MLD, such as ease of sample processing, superior ambient stability, and minimal carbon contamination. The incorporation of an oxide layer minimizes carbon contamination by facilitating attachment of carbon-free precursors or by impeding carbon diffusion. The oxide-MLD strategy allows selection of many inexpensive precursors and therefore allows application to both p- and n-doping. The phosphonic acid-functionalized SiO2 surfaces were investigated using X-ray photoelectron spectroscopy and attenuated total reflectance Fourier transform infrared spectroscopy, whereas doping was assessed using electrochemical capacitance voltage and Hall measurements

Stabilization of black phosphorus by sonication-assisted simultaneous exfoliation and functionalization

Black phosphorus (BP) has extraordinary properties, but its ambient instability remains a critical challenge. Functionalization has been employed to overcome the sensitivity of BP to ambient conditions while preserving its properties. Herein, a simultaneous exfoliation–functionalization process is reported that functionalizes BP flakes during exfoliation and thus provides increased protection, which can be attributed to minimal exposure of the flakes to ambient oxygen and water. A tetrabutylammonium salt was employed for intercalation of BP, resulting in the formation of flakes with large lateral dimensions. The addition of an aryl iodide or an aryl iodonium salt to the exfoliation solvent creates a scalable strategy for the production of functionalized few‐layer BP flakes. The ambient stability of functionalized BP was prolonged to a period of one week, as revealed by STEM, AFM, and X‐ray photoelectron spectroscopy

Evaluating the surface chemistry of black phosphorus during ambient degradation

Black Phosphorus (BP) is emerging as a promising candidate for electronic, optical and energy storage applications, however its poor ambient stability remains a critical challenge. Evaluation of few-layer liquid exfoliated BP during ambient exposure using x-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) allows its surface chemistry to be investigated. Oxidation of liquid exfoliated few-layer BP initially occurs through non-bridged oxide species, which convert to bridged oxide species after ambient exposure. We demonstrate the instability of these bridged oxide species which undergo hydrolysis to form volatile phosphorus oxides and evaporate from the BP surface. FTIR spectroscopy, scanning transmission electron microscopy and atomic force microscopy were used to confirm the formation of liquid oxides through a continuous oxidation cycle that results in the decomposition of BP. Furthermore, we show that the instability of few-layer BP originates from the formation of bridged oxide species

Crystallographically controlled synthesis of SnSe nanowires: potential in resistive memory devices

Here the controlled growth of SnSe nanowires by a liquid injection chemical vapor deposition (CVD) method employing a distorted octahedral [SnCl4{n BuSe(CH2)3Sen Bu}] single‐source diselenoether precursor is reported. CVD with this single‐source precursor allows morphological and compositional control of the SnSex nanostructures formed, including the transformation of SnSe2 nanoflakes into SnSe nanowires and again to SnSe nanoflakes with increasing growth temperature. Significantly, highly crystalline SnSe nanowires with an orthorhombic Pnma 62 crystal structure can be controllably synthesized in two growth directions, either or . The ability to tune the growth direction of SnSe will have important implications for devices constructed using these nanocrystals. The SnSe nanowires with a growth direction display a reversible polarity‐dependent memory switching ability, not previously reported for nanoscale SnSe. A resistive switching on/off ratio of 103 without the use of a current compliance limit is seen, illustrating the potential use of SnSe nanowires for low‐power nonvolatile memory applications

Flow synthesis of iodonium trifluoroacetates through direct oxidation of iodoarenes by Oxone®

Flow chemistry is considered to be a versatile and complementary methodology for the preparation of valuable organic compounds. We describe a straightforward approach for the synthesis of iodonium trifluoroacetates through the direct oxidation of iodoarenes in a simple flow reactor using an Oxone‐filled cartridge. Optimization has been carried out using the Nelder–Mead algorithm. The procedure allows a wide range of iodonium salts to be prepared from simple starting materials

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