In‐situ Messung dünner Schichten auf Architekturglas

For the deposition of modern coatings on architectural glass (energy‐saving, solar control, anti‐reflective), reactive magnetron sputtering plays an outstanding role. The production of these coatings by reactive sputtering requires a manufactoring equipment, that ensures high quality as well as efficient deposition of the coatings. Thin film measurement by in‐situ ellipsometry can very impressively used for monitoring and controlling the film properties, in particular in the case of more complex coatings. With regard to long‐term stability the in‐situ film measurement is of special importance with respect to the use of the novel mid‐frequency magnetron sputter technique. This technique allows the deposition rate to be increased up to 500 %, however, a dynamical plasma stabilization in the so called »transition mode« is necessary. Within the framework of a project supported by the BMBF, the spectroscopic ellipsometry was implemented on a large scale glass deposition plant (Semco Glasbeschichtung, Neubrandenburg) and was tested during the production. The investigations show that ellipsometry is outstandingly suitable for an accurate determination of the optical layer properties of coatings on architecture glass, even for complex layer systems. Therefore, the basis for an improvement of the efficiency of the plant is given.     

Untersuchung dünner Schichten mittels Röntgenreflektometrie

Thin film characterization by means of X‐ray reflectometry X‐ray reflectometry and diffractometry are widely used non‐destructive methods to characterize thin films in the total thickness range which is typically between 2nm and approximately 500nm. On special arrangements a resolution up to 1000nm layer thickness has been demonstrated. Layer stack morphology, surface topography, layer structure, material density, single layer or period thickness and surface and interface roughness are the typical structural parameters both of single layers and of multilayers which can be described by the measured data. The performance of the measurement setup is mainly influenced by the parameters of the incident X‐ray beam like beam divergence, monochromatism and photon energy. In the following the influence of the optical components in the beam path to angle and energy resolution of X‐ray reflectometry is discussed.     

Beitrag zum Studium des Bruchvorganges dünner Bitumenfilme

Contribution to Studies of fracture in thin bituminous films. A recently published theory of crack propagation in viscoelastic materials is briefly reviewed. This theory serves as a basis for a newly developed hypothesis describing the fracture process in thin bituminous films. Observation of fracture surfaces with the help of a scanning electron microscope showed that microcracks start from the weakest points (inhomogeneities) in the matrix. By increasing the external load disk-shaped cracks increase as a function of the applied load. Only when the critical mean crack diameter is reached macroscopie failure occurs. Fractographic methods proved to give detailed information about fracture process in thin bituminous films.     

Anlagenkonzept für die Abscheidung dünner Schichten durch Plasmapolymerisation

This plasma polymer layers are deposited by a plasma enhanced CVD process directly from the gas phase of an organic precursor (plasmapolymerization). Film growth rate is limited by the quantity of gas input. Plasmachemical conversion in the gas phase as well as at the film surface can be applied to affect film properties. The relation between the characteristic conversion time of the process and the application features of the plasma polymer layers lead to a vacuum technological concept for development and design making large scale applications in industry very predictable.     

Neue Möglichkeiten zur Charakterisierung dünner Schichten mit Indentermethoden

Novel Possibilities for Thin Film Characterisation Using Indentation Methods A novel methodology for the evaluation of the response of coated substrates to mechanical contact is presented which is based on the combination of a new theoretical method and high‐accuracy indentation experiments using a spherical diamond indenter. The concept may be extended in many respects and will be illustrated here only with few special examples: Using low loads, i. e. staying completely in the elastic region, the elastic parameters of film and substrate can be measured with high accuracy. When the indentation experiments is extended until failure of the coating substrate compound, the full stress and strain fields in three dimensions in the very moment of failure can be calculated. The knowledge of those fields enables one to draw conclusions on the relevant mechanisms. Once the failure mode has been identified, layer systems with optimum resistance to that failure mechanism can be found by theoretical simulations.     

Zerstöurungsfreie Prüfung dünner CFK-Laminate mit innenliegenden Fehlern

Nondestructive Testing of thin CFRP-laminates with Internal Flaws Carbon fiber reinforced plastics (CFRP) are more and more used for primary aircraft structures. Therefore, nondestructive testing is of increasing importance for quality control and maintenance. Test specimens with different flaws show the accuracy by which even very small flaws in CFRP laminates can be detected when using ultrasonic (US) and X-ray-techniques. The US-measurements (C-scans) were effected by a highly resolving US-flaw detector. Details of the system and of testing methods are described. The C-scans are compared with X-ray evaluations. Internal flaws which cannot be found in a normal X-ray image due to X-ray absorption were filled with a contrast agent (TBE); afterwards they appeared very clearly on the X-ray film. A comparison of nondestructive tests and between nondestructive and destructive tests showed a good agreement.     

Röntgendiagnostik plasma‐gestützt abgeschiedener dünner Schichten

X‐ray diagnostics of plasma deposited thin layers Grazing incidence x‐ray diffractometry (GIXD) and x‐ray reflectometry (XR) have been introduced as well suited tools for investigations of plasma deposited thin layers. They are non‐destructive techniques, therefore a sample can be reused and measured with other techniques. A combination of GIXD and XR can give a range of interesting information about chemical, physical and crystallographic properties of thin films. Conclusions can be drawn how plasma deposition techniques and plasma parameters influence the film growth. In three examples we present the analysis of phase and chemical composition, defect structure and measurements of kinetic process parameters.     

Funktionale Oberflächen auf Duplex‐Stahl durch Laserfeinbeschichten

Functional surfaces on duplex stainless steel by lasercladding The product‐lubricated axial and radial bearings installed in multistage high‐pressure pumps inevitably encounter severe mixed friction conditions as the pumps start and stop. This leads to extremely high tribological loads on the bearing components, compounded by the effects of a highly corrosive pumped fluid. The present paper describes a laser cladding process which produces near‐net‐shape coatings of new, highly corrosion and wear resistant functional layers which can be deposited directly on high‐alloy stainless steels without requiring additional buffer layers and without affecting the mechanical properties and corrosion resistance of the substrate. The results cover the solidification behaviour of the coatings as well as the microstructure resulting from various heat treatment conditions. In addition, the technological properties of the coatings and the resulting composites are discussed. The coating systems are tested as to their corrosion resistance and tribological characterization in a pump‐specific tribological system.     

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.     

Einfluss der chemischen Umgebung auf Morphologie und Struktur von Magnesiumhydroxid auf Magnesiumoberflächen

Influence of the Chemical Environment on the Morphology and Structure of Magnesium Hydroxide formed on Magnesium Surfaces Successful application of magnesium in metal construction is promoted by available methods for surface protection and, if needed, an electrical isolating layer between magnesium and other construction metals of composite materials [1]. Suitable materials for surface protection are polymer coatings, e. g. polymer paints. These coatings require a sufficiently corrosions resistant ground, which up to now normally is a environmentally dangerous, chromium‐containing conversion layer. In case of destruction of a conversion layer, caustic magnesium hydroxide is formed and responsible for a promoted delamination of various commercial polymer paints. Thus, development of a new magnesium – polymer – systems is of great interest. One probably successful possibility is a defined chemical attachment of molecular adhesion promoters to the magnesium conversion layers. These adhesion promoters should include a magnesium hydroxide specific group for a strong chemical attachment to magnesium conversion layer, which is hydrolytically stable in water, and additionally a second adhesive group at the other end of a hydrophobic spacer to ensure the attachment of a polymer. Direct attachment of these molecular adhesion promoters onto magnesium metal is not promising as all known magnesium organic compounds are hydrolytically instable [2]. As the hydroxide conversion coating is a substantial part of a magnesium‐polymer‐composite, the properties of the magnesium hydroxide layer have to be investigated and optimized depending on preparation conditions. In order to characterize the magnesium hydroxide conversion layer we use IR‐spectroscopy, quartz microbalance and Scanning Probe Microscopy. IR‐spectroscopic investigations show the presence of water in hydroxide conversion coatings formed at pH = 7–10. Conversion coatings prepared at pH > 12 are spectroscopically free of water. Taking into account the isoelectric point and the reactions resulting from a pH change, a model for the formation of the hydroxide layer is presented. This model explains the formation of a water free hydroxide layer at pH levels above 12 and the formation of water containing hydroxide layers below pH 12. The topography of the conversion layers is investigated by Scanning Probe Microscopy. If the conversion layer is formed in a solution with low pH a rough structure is built up compared to conversion layers, which are formed in solutions with high pH. These differences can be explained by taking into account the solubility of magnesium hydroxide and the change of OH⁻‐concentration in the solution due to different pH.     

Einflüsse auf die Kriechporenbildung und deren Nachweis bei warmfesten niedriglegierten CrMoV-Stählen

Effects on creep cavitation and determination of creep cavities on heat resistant low alloy CrMoV-steels The aim of this work is to describe the evolution of damage due to creep cavities under long-term creep conditions as well as to quantify it by metallographic methods. The chosen materials comprised the high temperature steels 12 CrMov 4 3 and 15 CrMoV 5 10. The investigations are made under consideration of unaxial stress, temperature, time, life-fraction, creep-strain and the initial microstructure.     

Realistische Modellierung der NIR/VIS/UV‐optischen Konstanten dünner optischer Schichten im Rahmen des Oszillatormodells

Modelling the NIR/VIS/UV optical constants of thin solid films: An oscillator model approach Based on a multioscillator approach, we demonstrate the determination of optical constants of different optical coating materials. The advanced LCalc‐software allows calculating the dielectric function as well as refractive index and extinction coefficient through a fit of transmittance and reflectance spectra measured at one or several angles of incidence. Sufficiently accurate spectrophotometric measurements are carried out by means of self‐developed VN‐ The thus obtained optical constants are automatically Kramers‐Kronig‐consistent and in reasonable correspondence to various kind of side information available about the coatings. This is demonstrated for dielectric oxide coatings as well as for one transparent conductive oxide (ITO) and a metal layer (aluminium). In application to reproducibility experiments, the method allows estimating process‐inherent stochastic variations in optical constants, which represent themselves an essential input for advanced computational manufacturing runs for design optimization prior to deposition.     

Der Einfluß der Porosität auf einige Eigenschaften von Wolfram/Kupfer-Kontaktwerkstoffen

The Influence of Porosity on a Few Properties of Tungsten/Copper Contact Materials . An investigation has been carried out on the influence of the amount of residual porosity on the electrical and mechanical properties of infiltrated tungsten/copper materials. By means of adding different quantities of infiltrating metal materials with a tungsten content of approximately 70 wt.% containing between 0,2 and 30% pores were produced. The following properties were measured for the different material specimens: are erosion rate, electrical conductivity, Vickers hardness number, and notch impact toughness. The arc erosion rate is not noticeably increased by pore contents up to 4%, all the other properties, however, are influenced considerably even by the smallest amount of measurable residual porosity. Thus it has to be concluded that infiltration with a slightly smaller quantity of infiltrating metal than that necessary to attain a pore-free material – a technique used occasionally in order to avoid the necessity of finishing the infiltrated parts – will lead to changes in quality.     

Der Einfluß der Haupt- und Seitenkerbung auf die Temperaturabhängigkeit der Kerbschlagarbeit

The effect of main notch and of side grooves on the temperature dependence of the absorbed energy in impact tests Charpy impact tests were performed on test pieces having different radii of curvature of base of main notch. Six series were sidegrooved and six series were without side grooves. The fracture mechanisms and the appearance of the fracture surfaces are discussed. It is shown that the common practice to assign lower shelf, transition range, and upper shelf in the absorbed energy-temperature curve to cleavage fracture, mixed fracture, and fibrous fracture is not always valid. Cleavage fracture may occur in the entire transition range and mixed fracture may take place in the upper shelf.