p‐TCOs für Transparente Elektronik

p‐type TCOs for use in transparent electronics In this article, a new type of semiconducting material is introduced. Transparent conducting thin films are already established in our everydaylife. But the type of these so‐called ?TCOs”? is dominated by electron transport, that means they are n‐type. To get transparent p‐n‐junctions and therefore transparent electronics, the missing part is a transparent p‐type material. Researchers all over the world have found different approach to produce this new generation of materials. At the Fraunhofer Institute for Surface Engineering and Thin Films (IST) in Braunschweig it is now possible to produce these kind of thin films as well.     

Kohlenstoffbasierte Beschichtungen für automotive‐Komponenten

Carbon‐based coatings for automotive components The outstanding properties of carbon‐based coatings are the low friction against steel and the wear resistance, interconnected with the high hardness. In lubricated systems coatings only work in the mixed and boundary friction regime; this means as long as primary body and counter body are still in contact. The properties of coatings can be adjusted in wide ranges. A purposeful adaptation requires that the tribological system is sufficiently well understood. It has been shown that solutions based on coatings are only sub‐optimal if the coating is only introduced at the end of the designphase. A greater benefit is obtained, when the scope for development as given by a coating is utilized already in the early design phase. The coating is accepted as a design element. To test the suitability of the selected coating quickly and inexpensively in advance, the usual standard laboratory tests are not always appropriate. A test set‐up has to be close enough to the application to generate useful results. These considerations are illustrated using the example of a piston pin coating. The roughness of the primary body and of the counter body is of particular importance for the adjustment of the coating system, when high loads are applied. The example presented here shows that the usual indicators for surface roughness like R_a and R_z are not always sufficient.     

Kollektorbeschichtungen für die EUV‐Lithografie

Collector Coatings for EUV Lithography Extreme ultraviolet lithography (EUVL) is the next generation lithogra phy method operating at the wavelength of 13.5 nm (14 times shorter than current lithography systems), enabling semiconductor scaling to resolutions of 22 nm and below [1]. This paper presents the successful coating of the world's largest ellipsoidal collector mirror for EUV radiation with a diameter of 660 mm ( Fig. 1 ). In order to achieve the required peak reflectivity of more than 65 %, the ellipsoidal collector was coated with a highly reflective, laterally graded multilayer using the dc magnetron sputtering system “NESSY”. A maximum reflectivity of the laterally graded multilayer of more than 65 % was achieved for radii smaller than 220 mm. For radii between 230 mm and 320 mm the reflectivity decreases to a minimum of 58 %. The targeted wavelength remains constant at (13.50 ± 0.05) nm over the entire collector surface which is well within the tight specifications for high volume manufacturing.     

Plasmaprozesse für 3D‐Formteile

Plasma treatment and coating processes for 3D parts Many articles of our daily use are only able to feature their outstanding performance due to innovative plasma surface treatments. Semiconductor components like flat panel displays, solar panels, DVD / Blu‐ray Discs, as well as optical components, coated glass panes, cutting tools and other components with reduced wearing are just a few examples. One important quality feature is to reach uniform properties over the entire surface to be treated. In case of planar or slightly curved surfaces this can be relatively easily achieved by using common plasma sources. For complex 3D parts, the effort required for uniform surface treatments greatly increases, and complex movements of the 3D parts are often required to achieve uniformity. This article deals with the plasma surface treatment and plasma coating of such complex 3D parts referring to some selected examples.     

PM‐Werkstoffe für warmgehende Werkzeuge

PM‐Materials for Hot Working Tools Tools and wear parts for compacting tools are subjected to high abrasive wear and mechanical loading at elevated temperatures. MMC's based in iron‐ or nickel with hard particles are developed and investigated. The materials were manufactured from powders by hot isostatic pressing (HIP) and subsequently heat treated. Diffusion between hard phases and metal matrix brings about certain micro structures which were tested with respect to the resistance against sliding abrasion at room and elevated temperatures. Three‐point bending tests and thermal cycling of the material was utilized to characterised the mechanical behaviour. Based on this results a toolkit for a roller press for briquetting was produced and brought into application.     

Anforderungen an Metalloxid‐Schichten für Interferenzoptik

Metal Oxide Films for Interference Optics: Demands on Quality – State of the Art in Production Demands on quality and stability of PVd‐metal oxide coatings are increasing with modern optical systems, complex structures and extension to short and long waves. Deposition requires always, independent on starting material, reactive technologies. Basic PVd‐processes are either fast running but low in particle energy (evaporation), or exactly the other way round (sputtering) or have disturbing side effects (arc ablation). It is shown how they are modified and improved to become effective in reliable and fast deposition of high quality, low defect films. This is performed by adding ions and plasma species or combining magnetic fields and operate the various hybrid processes in continuous or pulsed modes. Characteristic data of the processes are presented as well as properties of metal oxide films produced with energetic reactive, continuous and pulsed plasma processes.     

Selbsttrocknende Membran‐ Vakuumpumpen für feuchte Gase

Diaphragm vacuum pumps have proved their superiority as dry‐running systems over other types of vacuum pumps in many applications, and in particular in the medical, analysis, and process engineering sectors, as well as in the chemical industry. These pumps deliver the media without any contamination of content, have a high gas tightness, and can be designed as chemically resistant with regard to those parts which come in contact with the media. Although they are in principle relatively insensitive towards condensates which may be formed or conveyed with the media, liquids in the vapor or gas flow may be the cause for the prolongation of a vacuum process, which can be considerable and is certainly undesirable. This applies in particular to applications involving multi‐user vacuum systems in chemical laboratories, which under certain circumstances may contain very substantial volumes of condensates, and to the use of pumps in steam sterilizers (autoclaves) and vacuum drying cabinets. These examples of applications will be considered in greater detail hereinafter. The condensates which occur in the pump head of a diaphragm vacuum pump cause interference in that — due to re‐evaporation during the suction cycle — they incur a substantial reduction in the usable suction capacity of the pump. This problem can be resolved by means of a drying system for diaphragm vac uum pump heads. The drying system makes use in this case of the pressure differential which pertains between the pump chamber and the atmosphere outside the pump. The function of the drying system can be described as follows: A solenoid valve vents the pump head in a cyclic manner, with the result that liquid in the pump head will be blown out, while the process vacuum in the process engineering system will continue to be maintained. Diaphragm vacuum pumps equipped with this drying system have provided excellent results, for example in the chem ical laboratory, both in individual diaphragm vacuum pumps as well as in multi‐user vacuum systems. Extremely good experience has also been gained in the evacuation of sterilizer autoclaves and vacuum drying cabinets with the use of diaphragm vacuum pumps fitted with the drying system. When using the drying system on steam sterilizer autoclaves, another favorable effect is also encountered: The vapor fraction in the pumping medium is cooled in the diaphragm pump head to below the evaporation or boiling temperature, with the result that the vapour condenses. This reduces its volume to a fraction of the initial value, which is the equivalent of an additional suction capacity, in the same manner as with a condenser. The condensate which occurs with this process is blown out of the pump heads by the drying system, and, as a result, can no longer cause interference due to re‐evaporation.     

Organische UV‐Schutzschichten für die Polycarbonatverglasung

Organic UV‐protective coatings for polycarbonate glazing Polycarbonate as glazing material in outdoor applications requires functional UV protective and scratch resistant coatings. The vacuum coating technology offers a wide range of deposition processes to produce such complex coatings. The Fraunhofer IOF developed an effective UV protection by the deposition of organic UV absorbers. Thermal evaporated organic compounds were investigated as single layers and hybrid layers in a SiO₂ matrix. The UV‐stability of such coatings was increased significantly.     

Tribologische Sub‐Mikrometer Schichten für Mikrosysteme

With increasing interest in microelectromechanical systems (MEMS) a high demand on performance and lifetime arises. One option to improve this reliability is the optimization of friction and wear behaviour. Therefore we present a selection of well established systems that were scaled to serve as microtribological coatings. Hard and superhard coatings like DLC, CN_x, cBN and Alumina were investigated and optimized. For a better understanding of the tribological processes and the occuring effects in microsystems we used the macroscopic pin on disc test as well as nanoscale characterization like AFM based nanoindentation and a newly developed tape abrasive wear test.     

Zugkraft‐Lastenträger für Vakuumisolation

Tension Carrier and spacer for Vacuum Insulation and general mechanics (and heat brige free usage) A life long dream of researchers and developers of spacers for supported vacuum arrangements cam true and an easy to manufacture elementary Tension Carrier is now developed. It makes it possible, to carry the forces produced by pressure difference by elements, which are bearing tension forces only. Through that conductive heat transfer rates up to 1E‐6 W/mK and lower are attainable. The new Tension Carriers allow further an easy accomodation of unloaded radiation rejection means in evacuated room. Moreover this Tension Carriers have improved abilitys for faster evacuation and have great reserves for constructive and material adaptation in applications. Especially heat bridge free evacuated system embodiments will be achievable, but also sealed VIP‐Plates benefit from attainable improvement in performance and costcutting.     

Elektrodenauswahl für das WIG‐Unterwasser‐Schweißen

Selection of electrode for GTA‐Underwater Welding Reproducible good weld quality and economical benefit of underwater‐welding require a complete automation. For this purpose Gas Tungsten Arc‐welding (GTA or TIG) offers numerous advantages, especially for the root and the following hot pass run. Disadvantages of GTA‐welding are the low weld deposit rate and the limited lifetime of the tungsten electrode. Already small wear damages cause wide alterations of the arc under high surrounding pressure, so that a suited choice of the electrode enables to increase the productivity considerably. Therefore the influence of the electrode features on welding process, arc stability, arc ignition, weld geometry and electrode wear has been investigated. For quick and elementary selection of electrode an assessment catalogue was elaborated.     

Prüflecks für Schnüffel‐Lecksucher

In the testing of leak tightness and in the localisation of leaks by means of a test gas, proper operation and sensitivity of the employed instrument must be checked by a certified reference leak. In the so‐called sniffer mode of operation, the component under test is filled to overpressure with the test gas, so that in case of a leak there is a gas flow from the component to atmosphere. The atmospheric gas is sucked by the instrument and probed for its test gas content. For checking the instruments performance, commercial test leaks are available for various gas species, which deliver a well‐defined leakage. Construction and properties of such a test leak are described. The leak has an internal gas reservoir and a capillary as leak element. Because the inlet pressure at the capillary is kept constant by a pressure controller, the leakage remains constant over several years despite the gradual pressure decrease in the gas reservoir. The calibration of the leakage via the volume flow rate is described in detail. The volume flow rate can be measured by a liquid drop in a measuring capillary as well as a displacement piston in a dosing syringe.     

Hydroform‐Technologie für hoch belastbare Stab‐Knoten‐Bauweisen

Hydroforming Technology for Highly Loaded Truss Structures Truss constructions are often prefered because they can be built up highly variably starting with simple elements. In the present study light weight structures for heavy loads handling systems are considered. The hydroforming technology offers the possibility to manufacture highly precise stress adaptive tubes and nodes for such structures. The tubes and nodes are manufactured from thin walled tubes. However, the expenses for hydroformed parts are quite high. In the present paper possibilities are outlined to decrease these expenses significantly by reducing the number of different elements that are needed for the constructions down to a minimum, furtheron, by a careful optimization of the structures and their elements, and by the utilization of variable hydroforming tools. Of primary importance, however, is that the hydroformed structural elements can be highly loaded, that they safely operate during their service life and that they are resistant against environmental influences. For the realization of hydroform parts and tools an integrated design concept is proposed. The influence of hydroforming on microstructure is also considered.     

Neue Kapseltechnik für Diamantverbundwerkstoffe mittels PVD‐Verfahren

Novel encapsulation technique for diamond composites using PVD‐process For machining of mineral materials diamond tools consisting of a steel body combined with diamond impregnated segments are used. Frequently, these segments are hot pressed. Other process routes are pressureless sintering of green compacts partly combined with hot isostatic pressing and hot isostatic pressing of encapsulated powder mixtures. The compaction effect of hot isostatic pressing require a low porosity of sintered components realized by using ultra‐fine metal powder or an impermeable capsule made of metal or glass. The Institute of Materials Engineering pursues a novel process route by physical vapor deposition of a coating on pressureless sintered composites. The thin coating acts as a capsule and guarantees the pressure transfer in the following hot isostatic pressing process. Although bronze powders with particle sizes up to 90 μm are used, the manufacturing of diamond composites with low porosities is possible. In comparison to conventional encapsulation‐techniques the main advantages of this novel process route are the use of comparatively coarse metal powders and a larger geometric flexibility.     

PVD‐Nanocomposite‐Beschichtungen für die Zerspanungs‐ und Umformtechnik

PVD Nanocomposite coatings for the machine cutting and deformation technique Physically and chemically separated wear‐protection layers exhibit increasingly more complex structures. Similarly to the a coil of compact materials increase also here solutions develop as composite materials, which are offered in the form of Nanocomposites. An industrially available solution represents the system MeN/Si₃N₄. This is to be introduced concerning its characteristics as well as its application type within the range of the machine cutting and deformation technique.     

Reinigung von Vakuumbauteilen für UHV‐ und UCV‐Anwendungen

Cleaning of vacuum components for UHV and UCV applications Ultra‐clean vacuum components and assemblies are fundamental to some cutting edge high‐tech sectors like semiconductor industry, particle accelerators, and surface analytics. Exceptionally critical for these applications are particles that stick at the vacuum facing surfaces as well as desorption of water and hydrocarbons from the surfaces into the system, because this may interfere with the sensitive ultra‐high vacuum (UHV) and ultra‐clean vacuum (UCV) processes. In this contribution, some established cleaning methods and surface treatments are discussed with respect to their effect on reducing particle contamination and outgassing of water and organic compounds from stainless steel surfaces. It is clarified that the resulting cleanliness severely depends on the detailed steps during the surface treatment and subsequent cleaning. As a consequence, the discussed methods should be chosen and adapted with great care according to the specific demands of the final application area.