Simulation von Plasma‐Beschichtungsprozessen

Simulation of plasma deposition processes – a new design tool for vacuum and plasma technology In the course of the up‐scaling of industrial deposition methods, the demands on productivity as well as on precision are continuously increasing. Both requirements are conflictive, since e. g. an increase of the substrate size for higher productivity often involves homogeneity issues. The increasing complexity and size of coating machines hampers their further enhancement by pure empirical approaches. For this reason, the research and development on coating technology nowadays becomes more focused on simulation methods. At Fraunhofer institute for surface engineering and thin Films we have developed a particle‐in‐cell monte carlo simulation environment for transport phenomena and gas discharges in the low‐pressure regime. This tool can be used for predictions and optimizations in the development of new deposition sources, furthermore the general insight in plasma discharge mechanisms can be improved.     

Single‐ and Double‐Sided Chemical Functionalization of Bilayer Graphene

An experimental study on the interaction between the top and bottom layer of a chemically functionalized graphene bilayer by mild oxygen plasma is reported. Structural, chemical, and electrical properties are monitored using Raman spectroscopy, transport measurements, conductive atomic force microscopy and X‐ray photoelectron spectroscopy. Single‐ and double‐sided chemical functionalization are found to give very different results: single‐sided modified bilayers show relatively high mobility (200–600 cm² V^?1 s^?1 at room temperature) and a stable structure with a limited amount of defects, even after long plasma treatment (>60 s). This is attributed to preferential modification and limited coverage of the top layer during plasma exposure, while the bottom layer remains almost unperturbed. This could eventually lead to decoupling between top and bottom layers. Double‐sided chemical functionalization leads to a structure containing a high concentration of defects, very similar to graphene oxide. This opens the possibility to use plasma treatment not only for etching and patterning of graphene, but also to make heterostructures (through single‐sided modification of bilayers) for sensors and transistors and new graphene‐derivatives materials (through double‐sided modification).     

EUV‐Lithographie für zukünftige IC‐Chips. EUV‐Lithography for Future IC‐Technology

In the past the overwhelming success of the semiconductor industry was based on the realisation of ever smaller structures on chips in ever shorter periods. This allowed to increase the computational speed of the processors and the amount of data that can be stored in a memory chip. This reduction of the critical dimension was mastered within optical lithography by transition to smaller wavelengths. Those lithography technologies that are currently in the development or test phase, based on 193 nm or as well 157 nm laser sources, will not achieve dimensions around 50 nm. A fundamental change of technology is thus emerging. The currently favored basis for dimensions of 50 nm and below is EUV lithography, based on an optical technology with an exposure wavelength of 13,4 nm. This substantial reduction of the wavelength also implies a radical change of the methodology used up to now.     

Fluor‐Kohlenstoff‐Nanoschichten zur gezielten Oberflächenfunktionalisierung. Fluorine‐Carbon Nano Coatings for Specific Surface Functionalization

This article concerns some aspects of the research and development work, which is done within a project of the German Federal Ministry of Education and Research (BMBF) entitled: “nano functionalization of interfaces for data‐, textile‐, building‐, medicine‐, bio‐, and aerospace‐ technology”. In the following the broad field of applications of a surface modification on a nanometer scale is discussed. Also some scientific methods to characterize surface modifications of this kind are discussed. By means of low pressure plasma technology it is possible to functionalize surfaces and thus to well adjust their properties with respect to their application. This is done without changing the bulk material characteristics. The surfaces of the treated workpieces are covered by an ultrathin, i.e. only a few nanometer thick, fluorine‐carbon polymer layer by a plasma process. The physical and chemical surface properties, such as surface energy, roughness (on nanometer scale), dynamic wetting behaviour, or the adhesion properties against other materials, can be simple changed by varying the plasma process parameters. It is shown, that in future this surface modification will meet a broad field of applications.     

Multifunctional POSS‐Based Nano‐Photo‐Initiator for Overcoming the Oxygen Inhibition of Photo‐Polymerization and for Creating Self‐Wrinkled Patterns

Oxygen inhibition remains a challenge in photo‐curing technology despite the expenditure of considerable effort in developing a convenient, efficient, and low‐cost prevention method. Here, a novel strategy to prevent oxygen inhibition is presented; it is based on the self‐assembly of multifunctional nano‐photo‐initiators (F₂‐POSS‐(SH)₄‐TX/EDB) at the interface of air and the liquid monomer. These nano‐photo‐initiators consist of a thiol‐containing polyhedral oligomeric silsesquioxane (POSS) skeleton onto which fluorocarbon chains and thioxanthone and dimethylaminobenzoate (TX/EDB) photo‐initiator moieties are grafted. Real‐time Fourier‐transform infrared spectroscopy (FT‐IR) is used to investigate the photo‐polymerization of various acrylate monomers that are initiated by F₂‐POSS‐(SH)₄‐TX/EDB and its model analogues in air and in N₂. FT‐IR results show that F₂‐POSS‐(SH)₄‐TX/EDB decreases the effects of oxygen inhibition. X‐ray photo‐electron spectroscopy and atomic force microscopy reveal that the self‐assembly of F₂‐POSS‐(SH)₄‐TX/EDB at the air/(liquid monomer) interface forms a cross‐linked top layer via thiol–ene polymerization; this layer acts as a physical barrier against the diffusion of oxygen from the surface into the bulk layer. A mismatch in the shrinkage between the top and bulk layers arise as a result of the different types of photo‐cross‐linking reactions. Subsequently, the surface develops a wrinkled pattern with a low surface energy. This strategy exhibits considerable potential for preventing oxygen inhibition, and the wrinkled pattern may prove very useful in photo‐curing technology.     

Neuartige dekorative Farbschichten durch Plasma‐Beschichtung

Novel decorative color coatings using plasma deposition The market does not stop to demand for novel products. Only those who offer innovative products will explore new segments of the market and will not loose against the cheap suppliers from far eastern countries. This is even more important in the field of surface technology. Many products would not be competitive without plasma technology. Companies changing surfaces with plasma technology expect a noticeable growth between 20 and 50 % within the next years [1]. The deposition of thin layers using plasma makes it possible to obtain highly brilliant color coatings, specially mixed color effects (rainbow like) as well as color changes depending of the observation angle. These optical special effects would not be feasible with common painting techniques. Thus plasma deposition opens a new field for surface coating. In these layers the colors are created via interference effects of the light being used for illumination. They are called interference colors, well known to the most of us from thin oil films on a wet street.     

Hocheffiziente RF‐Impedanzanpassnetzwerke

Highly efficient rf impedance matching network for ICP sources Contrary to capacitive coupled plasmas (CCP) inductively coupled plasmas (ICP) offer a higher plasma density and therefore provide for higher deposition or etch rate and herewith a high efficiency for industrial low pressure plasma processes. In the following we will introduce a new impedance matching network, which was specifically developed for the requirements of the operation of inductive plasmas and especially for the use in an industrial application. For the application in production systems detailed knowledge of the plasma properties, like homogeneity and ion energy distribution is required. Plasma diagnostics and calculations of the plasma density distribution will be shown. Finally, the application in a production system, which fully automatically processes 1200 substrates of size 156 mm × 156 mm per hour on a compact 19 m² footprint, is introduced.     

Evaluation of mixed oxide formation and sintering behavior in thermal barrier coatings on nickel‐based superalloy

Thermal barrier coatings are widely used in aircraft turbines to protect nickel‐based superalloys from the effect of high temperature oxidation and hot corrosion. In this study, both NiCrAlY bond coat and yttria‐stabilized zirconia top coat were deposited using atmospheric plasma spray technique. After coating production, specimens were exposed to oxidation in air atmosphere at 900 °C, 1000 °C and 1100 °C for different periods of time up to 50 h. Microstructural transformations in the ceramic top coat and growth behavior of the thermally grown oxide layer were examined using scanning electron microscopy, porosity calculation, elemental mapping and hardness measurement. Formation of different types of oxides in the thermally grown oxide layer shows that this process strongly depends on deposition technique as well as on oxidation time and temperature. Hardness values of the top coat increased with a decrease in the porosity of the top coat. Uniformity and homogeneity of the thermally grown oxide layer and densification of the top coat were evaluated in terms of the structural durability of thermal barrier coating systems.     

Mechanically Switchable Biocide Plasma‐Polymer Coatings for Biomaterials

Silver nanoparticles are enclosed between two plasma‐polymer layers. We show that the second cross‐linked plasma‐polymer network acts as a barrier and significantly reduces the delivery of the silver nanoparticles into a surrounding aqueous environment. When the film is stretched, cracks appear in the plasma‐polymer layer, which allow an increase in the release of the silver. When the system returns to its initial length, the release is reduced because of the cracks' closure. The principle is described and the release of silver is evaluated under mechanical stimuli cycles. The antibacterial effect is stopped by the barrier of the plasma‐polymer layer but restored by stretching the coated material.     

Anti‐Eis‐Oberflächenbeschichtungen

Anti‐icing coating — optimization by means of plasma technology Ice on surfaces can significantly limit the function of devices and has to be removed by processes with high energy consumption. E. g., the formation of ice on rotor blades of wind turbines is not desired, on the wings of aircrafts it is even dangerous. With the aid of plasma technology, the Fraunhofer IGB has developed an anti‐icing coating for polymeric surfaces. Water‐repellent micro‐ and nanostructured coatings are applied to polymer foils made of impact‐resistant and shockproof polyurethane. Optimization of various process parameters has made it possible to produce ultra‐thin coatings, which reduces the ice's adhesion by over 90 percent. The new nanostructured foils open a wide range of applications.     

Tubular 3D Resistive Random Access Memory Based on Rolled‐Up h‐BN Tube

Due to their advantages compared with planar structures, rolled‐up tubes have been applied in many fields, such as field‐effect transistors, compact capacitors, inductors, and integrative sensors. On the other hand, because of its perfect insulating nature, ultrahigh mechanical strength and atomic thickness property, 2D hexagonal boron nitride (h‐BN) is a very suitable material for rolled‐up memory applications. In this work, a tubular 3D resistive random access memory (RRAM) device based on rolled‐up h‐BN tube is realized, which is achieved by self‐rolled‐up technology. The tubular RRAM device exhibits bipolar resistive switching behavior, nonvolatile data storage ability, and satisfactorily low programming current compared with other 2D material‐based RRAM devices. Moreover, by releasing from the substrate, the footprint area of the tubular device is reduced by six times. This tubular RRAM device has great potential for increasing the data storage density, lowering the power consumption, and may be applied in the fields of rolled‐up systems and sensing‐storage integration.     

Infrarot‐Laserabsorptionsspektroskopie mit Quantenkaskadenlasern in der industriellen Anwendung

Infrared laser absorption spectroscopy with quantum cascade lasers in industrial application Spectroscopic methods for gas analysis and plasma diagnostics in the field of the mid infrared spectral range (MIR) were lacking in sufficient time resolution up to now, they were cumbersome and not robust enough or simply too expensive. Through quantum cascade lasers as radiation source the application of the MIR absorption spectroscopy in the industry can be revolutionized. Although the industrial use in the plasma process is still in its infancy, their enormous potential is already evident, as demonstrated by measurements on plasma etching systems in the semiconductor industry, which is impressively documented.     

Kalte Normaldruck‐Jetplasmen zur lokalen Oberflächenbehandlung

Cold non‐thermal plasma jets for local surface treatment under normal pressure Plasmas at normal pressure are of considerable interest for surface technology because the industrial application requires no vacuum devices. Among other approaches, cold non‐thermal plasma jets represent an emerging technique to generate plasmas at normal pressure with attractive advantages. They allow ambient process temperatures and require only moderate operating voltages (1.5‐2.5 kV). They offer the advantage that the treated surfaces are not placed between the electrodes thus favoring local treatment of non flat, structured 3D surfaces. Moreover, the dimension of the sources is scalable and their integration into automated processes is simple. A capacitively coupled version (27.12 MHz) of a cold plasma jet suitable for surface treatment at atmospheric pressure is presented along with its plasma physical and technical properties and a series of successful applications, including plasma activation of surfaces for increasing printability, adhesion control, surface cleaning, microfluidics, decontamination, its use in plasmamedicine and for deposition of thin SiO₂ films as protective coatings. The device allows the operation with rare gases (e.g. Ar) and reactive gases as N₂, air or admixtures of silicon‐containing compounds.     

Isomery‐Dependent Miscibility Enables High‐Performance All‐Small‐Molecule Solar Cells

Nonfullerene polymer solar cells develop quickly. However, nonfullerene small‐molecule solar cells (NF‐SMSCs) still show relatively inferior performance, attributing to the lack of comprehensive understanding of the structure–performance relationship. To address this issue, two isomeric small‐molecule acceptors, NBDTP‐F_out and NBDTP‐F_in, with varied oxygen position in the benzodi(thienopyran) (BDTP) core are designed and synthesized. When blended with molecular donor BDT3TR‐SF, devices based on the two isomeric acceptors show disparate photovoltaic performance. Fabricated with an eco‐friendly processing solvent (tetrahydrofuran), the BDT3TR‐SF:NBDTP‐F_out blend delivers a high power conversion efficiency of 11.2%, ranked to the top values reported to date, while the BDT3TR‐SF:NBDTP‐F_in blend almost shows no photovoltaic response (0.02%). With detailed investigations on inherent optoelectronic processes as well as morphological evolution, this performance disparity is correlated to the interfacial tension of the two combinations and concludes that proper interfacial tension is a key factor for effective phase separation, optimal blend morphology, and superior performance, which can be achieved by the “isomerization” design on molecular acceptors. This work reveals the importance of modulating the materials miscibility by interfacial‐tension‐oriented molecular design, which provides a general guideline toward efficient NF‐SMSCs.     

Dual‐pathway DenseNets with fully lateral connections for multimodal brain tumor segmentation

Multimodal medical image data provide different structured and functional information, which helps segment brain tumor and gets a reliable and accurate diagnosis. Segmenting brain tumors in magnetic resonance imaging (MRI) is a challenging task because brain tumors can be at any location with changeable shape and size. Existing deep neural networks for brain tumor segmentation use few connections to fuse multilevel information. To make use of multilevel information from multimodal MRIs, we propose dual‐pathway DenseNets with fully lateral connections (DP‐DenseNets), a three‐dimensional (3D) fully convolutional neural network that uses dense connectivity to construct dual‐pathway architecture to multimodal brain tumor segmentation problem. Each two similar imaging modalities have a pathway, for one thing, the bottom‐up pathway with dense connectivity is developed for extracting features; another, the top‐down pathway concatenates the features of the bottom‐up pathway in all layers. Dual pathways with different loss functions and fully lateral connectivity from the bottom‐up pathway to the top‐down pathway provide an abundant combination of different levels of features. Comparing to these fusion schemes such as input‐level fusion and later‐level fusion, this architecture leverages semantics from low to high levels, which is provided by fully lateral connectivity. Our model is evaluated on the dataset from Brain Tumor Segmentation Challenge 2017 (BRATS 2017), and the experiments show that our method achieves better performance than other 3D networks.     

EPX ‐ die Ein‐Pumpen‐Lösung

A single dry pump mechanism capable of reaching high vacuum and itself exhausting to atmospheric pressure is considered as a ’?vacuum technology panacea’. The development and deployment of a single‐shaft, high‐speed EPX dry pump has gone some considerable way to achieving this goal. This article describes the stages in its development history and applications.     

A Parallel Strategy for the Logical‐probabilistic Calculus‐based Method to Calculate Two‐terminal Reliability

The theory of network reliability has been applied to many complicated network structures, such as computer and communication networks, piping systems, electricity networks, and traffic networks. The theory is used to evaluate the operational performance of networks that can be modeled by probabilistic graphs. Although evaluating network reliability is an Non‐deterministic Polynomial‐time hard problem, numerous solutions have been proposed. However, most of them are based on sequential computing, which under‐utilizes the benefits of multi‐core processor architectures. This paper addresses this limitation by proposing an efficient strategy for calculating the two‐terminal (terminal‐pair) reliability of a binary‐state network that uses parallel computing. Existing methods are analyzed. Then, an efficient method for calculating terminal‐pair reliability based on logical‐probabilistic calculus is proposed. Finally, a parallel version of the proposed algorithm is developed. This is the first study to implement an algorithm for estimating terminal‐pair reliability in parallel on multi‐core processor architectures. The experimental results show that the proposed algorithm and its parallel version outperform an existing sequential algorithm in terms of execution time. Copyright © 2015 John Wiley & Sons, Ltd.     

Pick‐and‐Place Assembly of Single Microtubules

Intracellular transport is affected by the filament network in the densely packed cytoplasm. Biophysical studies focusing on intracellular transport based on microtubule–kinesin system frequently use in vitro motility assays, which are performed either on individual microtubules or on random (or simple) microtubule networks. Assembling intricate networks with high flexibility requires the manipulation of 25 nm diameter microtubules individually, which can be achieved through the use of pick‐and‐place assembly. Although widely used to assemble tiny objects, pick‐and‐place is not a common practice for the manipulation of biological materials. Using the high‐level handling capabilities of microelectromechanical systems (MEMS) technology, tweezers are designed and fabricated to pick and place single microtubule filaments. Repeated picking and placing cycles provide a multilayered and multidirectional microtubule network even for different surface topographies. On‐demand assembly of microtubules forms crossings at desired angles for biophysical studies as well as complex networks that can be used as nanotransport systems.     

Facile Plasma‐Enhanced Deposition of Ultrathin Crosslinked Amino Acid Films for Conformal Biometallization

A novel method for the facile fabrication of conformal, ultrathin, and uniform synthetic amino acid coatings on a variety of practical surfaces by plasma‐enhanced chemical vapor deposition is introduced. Tyrosine, which is utilized as an agent to reduce gold nanoparticles from solution, is sublimed into the plasma field and directly deposited on a variety of substrates to form a homogeneous, conformal, and robust polyamino acid coating in a one‐step, solvent‐free process. This approach is applicable to many practical surfaces and allows surface‐induced biometallization while avoiding multiple wet‐chemistry treatments that can damage many soft materials. Moreover, by placing a mask over the substrate during deposition, the tyrosine coating can be micropatterned. Upon its exposure to a solution of gold chloride, a network of gold nanoparticles forms on the surface, replicating the initial micropattern. This method of templated biometallization is adaptable to a variety of practical inorganic and organic substrates, such as silicon, glass, nitrocellulose, polystyrene, polydimethylsiloxane, polytetrafluoroethylene, polyethylene, and woven silk fibers. No special pretreatment is necessary, and the technique results in a rapid, conformal amino acid coating that can be utilized for further biometallization.