Reaktives Magnetronsputtern von Dünnschichtsolarzellen

Reactive Magnetron Sputtering of Thin Film Solar Cells We show that reactive magnetron sputtering is well suited to deposit CuInS₂‐thin film absorber layers of high electronic quality. Using metallic targets and substrate temperatures below 500 °C, compact films with grain sizes in the micrometer range can be obtained. The structural and electronic properties of these layers are comparable to CuInS₂ thin films prepared by a 2‐step sulfurization process, which is being commercialized at present. In particular, the reactively sputtered films show minority carrier diffusion lengths larger than the layer thickness (≈ 2μm). This results in solar cells with conversion efficiences larger than 10 %, comparable to the best conversion efficiencies for CuInS₂‐solar cells obtained from other deposition processes. These results are promising for the potential application of magnetron sputtering as a large area deposition process for absorber layers in thin film solar cells.     

Dünnschichtsolarzellen

Thin Film Solar Cells The direct conversion of sunlight into electricity — photovoltaics (PV) — has emerged as a strongly growing market during the past years. Today, more than 80 % of the world market is supplied by solar modules based on mono‐ or polycrystalline silicon wafers. Thin‐film solar cells promise significantly lower costs for photovoltaic energy conversion, and thus will probably dominate the PV‐market in the future. Consequently, the production of thin film solar cells will lead to key technologies of the 21^st century. This article addresses the three most advanced types of thin‐film cells describing the status of these technologies at the laboratory level, in pilot production, and in first production lines. The challenges along the way from laboratory developments towards mass production are discussed, fo cusing on the central role of the vacuum‐based technologies applied for thin film deposition.     

Raster-Tunnel-Mikroskopie zur Untersuchung und Modifizierung von Festkörperoberflächen

We present a short review of the capabilities and prospects offered by the scanning tunneling microscopy (STM). Ultra-high vacuum — in general not necessary for STM operation at all — ensures without doubt well-defined surface and tunneling conditions. The latter are especially important for atomic resolution and spectroscopic applications. Shining examples selected from an almost exhaustiveless amount of original papers illustrate the new quality in local surface structural analysis, spectroscopy and modification achieved due to the establishment of STM and related scanning probe techniques.     

Einsatz physikalischer Analysemethoden zur Charakterisierung von dünnen Schichten und Grenzflächen in der Halbleiterindustrie

Characterization of thin films and interfaces are necessary in semiconductor industry to ensure high yields and the required reliability of the products. Requirements to thin film and interface analysis are reviewed, and typical applications in semiconductor industry are shown. Thin film characteristics which have to be determined using physical analysis techniques are film geometry, surface and interface roughness, chemical composition, and microstructure. Advances in physical failure analysis are essential to the reduction of feature size and introduction of advanced materials and processes for future technology generations. Future trends are discussed. To reduce the time for problem solving in the manufacturing process, out of‐fab characterization tools will partly move to“at‐line” labs which are located next to or sometimes inside the cleanroom.     

Untersuchung der Verteilung und Intensität filamentierter Barrierenplasmen für die Behandlung von Oberflächen

The application of barrier discharges at atmospheric pressure in air expands on the market of plasma technology, because it is an ecological and cost‐effective alternative to other processes of surface treatment. These plasmas usually consist of a multitude of spatially and temporally localized filaments, whose distribution should be as even as possible for homogeneous treatment. This holds especially for the plasma treatment of sensitive goods such as wool or other textiles. In equipment for continuous pass of material the barrier arrangements often consist of a system cylinder – cylinder or cylinder – plane, whereby the gap width changes locally. Space distribution and intensity of filaments has been investigated by means of short‐time photography and spatially resolved measurement of current distribution and energy distribution derived from it. The local dependency found can be explained by means of a capacitive equivalent circuit.     

Tribologische Untersuchung bionischer und mikrostrukturierter Funktionsflächen

An established concept adjusting tribological properties and for increasing the wear resistance is presented by coatings. In addition to the material adaption of surfaces, there are efforts of applying structures on tool active parts in order to allow a further adjustment on the property profile. For this reason, the presented article investigates the influence of bionic and technologically textured surfaces on the friction and wear behavior with and without near‐net shaped wear‐resistant PVD coatings. Based on the example of nature, a honeycombed surface structure discovered on the head of scarab beetles as well as a dimple structure optimized for the manufacturing time were transferred on HSS steel by means of micro‐milling. The analyses focus on the influence of the surface structures, the effects of PVD coatings and their interactions on the friction and wear behavior. The investigations show that the tribological properties depend on each surface structure and the material pairing. Both the technological and the bionic structures show a reduction of the friction coefficient in combination with the material pairing 100Cr6 and WCCo compared to polished samples. Furthermore, it is shown that the CrAlN coating has no influence on the friction behavior, but rather leads to the desired increase in the wear resistance.     

Klebflächenvorbehandlung von Aluminiumoberflächen mit SIP‐Haftvermittler

Surface pretreatment for adhesive bonding of aluminium with adhesive mediator SIP The present contribution describes the influence of different surface pretreatments including adhesive mediator SIP for adhesive bonding of aluminium alloy AlMg4,5Mn0,4. The investigations were performed using two cold hardening two‐components epoxy‐adhesives, one hot hardening one‐component epoxy‐adhesive and one cold hardening two‐components polyurethane‐adhesive. The adhesive bonds with epoxy‐adhesives show after three‐step pretreatment degreasing + corundblasting + SIP coating the highest adhesive strength values whereas adhesive bonds with polyurethane‐adhesive showed a decrease of bond strength as compared with the delivering surface condition.     

Nanostrukturierung von Kupferoberflächen durch Sauerstoff‐induzierte Rekonstruktionen

Nanostructuring of Copper Surfaces by means of Oxygen induced Reconstructions For metal single crystals the topography of vicinal surfaces can be changed in a controlled fashion by means of oxygen adsorption. This self‐organized phenomenon will be demonstrated for several vicinal copper surfaces. For densely packed copper surfaces with terrace lengths of ≤ 1 nm oxygen adsorption causes a doubling of terrace length and step height, whereas an oxygen‐induced mesoscopic faceting into periodic nano‐stripes is observed for regular monoatomic stepped surfaces with longer terraces. The width of the resulting nano‐stripes depends on the orientation of the clean vicinal surfaces and values of 10 to 50 nm have been observed. The thermal stability of the surfaces is found to increase with the stripes width, some structures are stable for temperatures up to 800 K.     

Untersuchung von Oberflächenschutzschichten von Gasturbinenlegierungen

Investigations on protective coatings on gasturbine alloys. It has been found by investigations of specimens of a combustion chamber pilot plant and also by experiences with gasturbines that aluminide or chromium aluminide coatings are only slightly protective under working conditions of industrial gasturbines. Chromium coatings have a distinctive better protective efficacy and are surpassed in this quality by silicide coatings. It was possible to give information on the development of silicide phases on Nimonic 105. Under the conditions of corrosive attack a surface layer of Nickelolivine is formed and the silicide phases are changed in direction of ternary phases. Even when chromium sulfides are formed in the silicide layer the specimens are stable under the test conditions. By investigations on an airfoil made from B 1900 with a protective coating of Aluminium and Silicon the presence is shown of a ternary Laves phase with Silicon.     

Klebflächenvorbehandlung von Aluminiumoberflächen mit Haftvermittler

Surface pretreatment for adhesive bonding of aluminum with adhesive mediator The influence of three steps pretreatment degreasing, blasting and primer and the two steps pretreatment degreasing and blasting on the adhesive behaviour of aluminum alloy AlMg4,5Mn0,5 were investigated. The investigations were preformed using two cold hardening two‐components epoxy adhesives, one hot hardening one‐component epoxy adhesive and one cold hardening two‐components polyurethane adhesive. The three steps pretreatment indicate that the adhesion bonding strength by epoxy adhesives are higher than that by two steps pretreatment. On the other hand, the adhesion bonding strength was similar by using polyurethane adhesive independence of the pretreatment method. Leaving out the pretreatment step degreasing after corund blasting caused by using, PU, EP 2 and EP 3 adhesives a significant decreasing of the bonding strength in comparison with the only degreased specimen. This degreasing process was used to remove the residual blasting medium from the aluminum surfaces after blasting. The topographical structure of the surfaces after corund blasting was covered by further pretreatment with primer as a consequence of higher primer viscosity, which causes a decreasing in the surface roughness. The chemical composition of pretreated surfaces by three steps was different from that by two steps.     

Veränderung von Stahloberflächen durch Reibung

Steel Surfaces after Fricton Processes. Steel surfaces which have been treated by friction under different conditions are investigated by scanning-electron-microscopy. The well-Known differences in the treatment by either reciprocating or continuous sliding may be separated in pictures of high magnification very accurately. Liquid lubricants during boundary lubrication from layers of certain solidity on the surfaces. The addition of antiwear-additives gives a better adhesion of the layers on the substrate. The behaviour of additives containing phosphorus are investigated thoroughly and compared with competing results given in the literature. It is stated by magnified surface pictures that the original conditions of the surfaces have minor influence on the wear process.     

Oberflächenmodifizierung von Titan zur Verbesserung der Grenzflächenverträglichkeit

Surface Modification of Titanium for Improvement of the Interfacial Biocompatibility We report the CVD‐polymerisation of amino‐functionalized [2,2]‐paracyclophane for polymer coating and functionalization of titanium surfaces. Additionally, the functionalization was carried out by silanization with 3‐aminopropyl‐triethoxysilane. The generated amino‐groups were used for covalent immobilization of bioactive substances to stimulate the adhesion and growth of osteoblasts. As bioactive substances the pentapeptide GRGDS and the growth factor BMP‐2 were chosen. The covalent bonding was achieved by activation with hexamethylene diisocyanate. Each modification step was characterized by X‐ray‐photoelectron‐spectroscopy (XPS), atomic force microscopy (AFM) and contact angle measurements. The covalent bonding of the bioactive substances was proven by radiolabelling and surface‐MALDI‐ToF‐MS. In vitro‐biocompatibility tests with primary, human osteoblasts demonstrated the improved cell adhesion and spreading on the bioactive modified titanium surfaces.