Lost in reciprocal space? Determination of the scattering condition in spot profile analysis low-energy electron diffraction

The precise knowledge of the diffraction condition, i.e., the angle of incidence and electron energy, is crucial for the study of surface morphology through spot profile analysis low-energy electron diffraction (LEED). We demonstrate four different procedures to determine the diffraction condition: employing the distortion of the LEED pattern under large angles of incidence, the layer-by-layer growth oscillations during homoepitaxial growth, a G(S) analysis of a rough surface, and the intersection of facet rods with 3D Bragg conditions.     

Analysing the Combined Health,Social and Economic Impacts of the Corovanvirus Pandemic Using Agent-Based Social Simulation

Minds and Machines - During the COVID-19 crisis there have been many difficult decisions governments and other decision makers had to make. E.g. do we go for a total lock down or keep schools open?...     

Vergleichende experimentelle und numerische Untersuchungen zum schwingungsüberlagerten Pressen zweier Pulvermaterialien

The pressing process is of special importance for the production chain of powder‐metallurgically produced components because in this production step the density distribution and thus the specific characteristics are set significantly. Especially the inevitable friction between the forming tools and the powder body leads to density gradients, which in turn cause sintering distortions and thus inhomogeneous material properties within the component. Therefore, the aim of the presented work was the systematic investigation on powder pressing with superimposed oscillations for the production of powder‐metallurgically produced components in order to reduce friction‐related density gradients. Subjects of the investigations were an aluminum powder (Alumix 13, ECKA) and a mixture of a abrasives and bond (Comet grinding wheels) as it is used for the production of ceramic bond grinding wheels. The results allow different material‐related conclusions regarding the positive effects of superimposed oscillations on the pressing process. Thus, the existence of a favorable oscillation frequency of about 60 Hz for the investigated abrasive/bond mixture could be proven. Above that, experimental and numerical investigations showed that, with an adequate oscillation frequency, density distributions can be achieved which otherwise can only be observed for the significantly more complex double action pressing.     

Electrical and Optical Properties of Transparent Conducting Homologous Compounds in the Indium–Gallium–Zinc Oxide System

The homologous compounds In_{1− x} Ga_{1+ x} O₃(ZnO) _k (where k = 1, 2, or 3) were prepared at a temperature of 1400°C. The solubility limits (as determined via X-ray diffractometry) were 0.47 < [In]/([In] + [Ga]) < 0.67 for the k = 1 member, 0.35 < [In]/([In]+[Ga]) < 0.77 for the k = 2 member, and 0.29 < [In]/([In]+[Ga]) < 1.00 for the k = 3 member. Four-point-conductivity and diffuse-reflectance measurements were performed on as-fired and reduced samples. The band gap that was determined from diffuse reflectance increased as the Ga³⁺ content increased and k decreased. The conductivity increased as k decreased and the In³⁺ content increased. A maximum conductivity of 250 S/cm was obtained for k = 3 and [In]/([In]+[Ga]) = 1 after reduction. The minimum absorption edge of 325 nm was obtained for k = 2 and [In]/([In]+[Ga]) = 0.35 prior to reduction. The potential for metastable phases in the In-Ga-Zn-O system with enhanced transparent-conducting properties has been discussed.     

Fatigue analysis of a mechanical press by means of the hybrid multi-body simulation

During the past decade in the automotive industry more and more conventional sheet metal components were replaced by high-strength sheet metal components. The processing of these modern sheet metals lead to an increase of the loads applied to the metal forming machines. In comparison to conventional sheet metals an extensive cutting-shock can be observed while cutting high-strength sheet metals. Hence, the components of the press start to oscillate and therefore the possibility of an early crack initiation increases. Thus, it has become necessary to investigate the specific demands while cutting modern sheet metals and take them into account during the design process of further presses. Within the framework of the presented project, conventional as well as high-strength sheet metals were cut and their loads were recorded. Additionally, a hybrid multi-body simulation model of a mechanical press was established and validated by means of measurements at a real press available at the Institute of Forming Technology and Machines (IFUM). Subsequently, the multi-body simulation model was coupled with a fatigue analysis software package. By means of the coupled simulation the fatigue life of the structural components of the press was determined. The entire approach was validated by means of test structures. The test structures were designed for a short fatigue life, manufactured and mounted the press available at the IFUM. A good correlation of the virtually determined and real fatigue life of the test structures was achieved.     

Control of topography and morphology for channel SiGe by in-situ HCl etching for future CMOS technologies with high-K metal gate

In high-K metal gate-first integration for future CMOS technologies an epitaxial SiGe layer in the P-channel is applied to modulate V_T. This results in an unwanted elevation of the P-channel challenging particularly gate patterning. In this work, an in-situ HCl etching process prior to deposition of the channel SiGe for gate-first integration of HKMG has been studied. By in-situ HCl etching prior to epitaxial deposition (recessed cSiGe) the topography is clearly reduced with excellent epitaxial quality. The morphology of channel SiGe particularly for very small feature sizes is significantly improved by recessing the P-channel prior to epitaxial deposition. The flat topography shows a clear benefit for the gate-first integration. The topography driven P-channel leakage was reduced by one order of magnitude for recessed channel SiGe.     

Flame Synthesis of Nanoparticles

An overview of recent advances in the synthesis of nanoparticles by flame aerosol processes is given. In flame processes with gaseous precursors emphasis is placed on reactant mixing and composition, additives, and external electric fields for control of product characteristics. Thermophoretic sampling can monitor the formation and growth of nanoparticles, while the corresponding temperature history can be obtained by non‐intrusive Fourier transform infrared spectroscopy. Furthermore, synthesis of composite nanoparticles for various applications is addressed such as in reinforcement or catalysis as well as for scale‐up from 1 to 700 g/h of silica‐carbon nanostructured particles. In flame processes with liquid precursors using the so‐called flame spray pyrolysis (FSP), emphasis is placed on reactant and fuel composition. The FSP processes are quite attractive as they can employ a wide array of precursors, so a broad spectrum of new nanosized powders can be synthesized. Computational fluid dynamics (CFD) in combination with gas‐phase particle formation models offer unique possibilities for improvement and possible new designs for flame reactors.     

Identification of reflected, scaled, translated, and rotated objects from their radon projections

In this paper, we present a method for identification of binary objects from a given set of radon projections. Given a suitably regular 2-D function f, we form a new function g from f by using the operations of reflection, scaling, translation, and rotation. We show how the radon projections of g are related to those of f and devise a procedure that can be used to determine the parameters from the radon projections of f and g. We illustrate this process using a family of block images that include common 7 x 5 pixel representations for the letters A, B,....., Z.