Abscheidung von dekorativen Schichten mittels PVD‐/CVD‐Verfahren

Deposition of decorative coatings using PVD/CVD methods Decorative surface treatment of consumer goods has a cross‐sectional function, because of its many application in different industries. Beneath the classical methods as lacquering and electrochemical graftage, vacuum‐based methods – named with the acronym PVD and CVD – have definitely established itself up to now. For the last two methods, the future market will have a good growth potential in the field of decorative surface treatment. One reason for this is, that nowadays the product differentiation is very important for the marketing and this takes place more and more via “design” and to a lesser extent via the functionality of a product. The following article gives an overview about the possibilities of decorative coating deposition using PVD/CVD methods. Attention is paid on colour mechanisms, colour measurement as well as on resulting colours.     

Anforderungen und Bewertung dünner Schichten im tribologischen Einsatz

Demands and assessment of thin films in tribological applications Thin films for tribological use have been supported intensively in the last years and decades. For this reason lots of single results exist in this field of activity. But until now for engineers a handy und reliable method for the development of practical solutions is not available. The literature quoted at the end of this article deals with this problem and points out possibilities. The following paper presents selected results. Single aspects are here in this consequence only described without detailed documentation. To do this the quoted literature offers further information concerning the application of hard coatings and it refers to over 900 corresponding publications. Missing data on test parameters or boundary conditions of the test procedures as well as detailed information on all presented aspects are written down there. Tables to do selections and assessments qualify the reference as a useful handbook for the application of thin hard coatings in theory and practice. The author is pleased to help you to get the complete publication.     

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.     

Elektronenbeugung zur Analyse dünner Funktionsschichten

Electron Diffraction for Analysis of thin Functional Layers A short history of the diffraction techniques in crystallography is given and the basics of electron diffraction in transmission electron microscopy are explained: electrons as waves, Bragg's law, selected area and convergent beam electron diffraction. The possibilities of the often used selected area electron diffraction are demonstrated by two typical examples: determination of the crystallographic orientation in single crystalline layers (piezoelectric LiTaO₃) and phase analysis in polycrystalline structures (Ni‐Al‐O hard coatings).     

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.     

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.     

Einfluss der PVD‐Prozessparameter auf die Schichtnukleation und Struktur von CrN‐Schichten

Störstellen in Bauteiloberflächen wirken sich negativ auf die Schichtnukleation bei PVD‐Schichtsystemen aus. Sie können im anschließenden Schichtwachstum zu Defekten in der Schichtstruktur führen. Die Konsequenz ist eine Minderung der lokalen Haftfestigkeit, höhere Reibwerte und Fehlstellen in der Schicht. Diese begünstigen in korrosiven Medien die Entstehung von Korrosion. CrN‐Schichten sind für ihre hohe Härte und ihre guten Verschleißeigenschaften bekannt. Zudem weisen sie eine bessere Korrosionsbeständigkeit als Titan basierte Nitride auf. Die strukturellen und mechanischen Eigenschaften dieser Schichtsysteme können unter anderem durch die Veränderung der Biasspannung und des Stickstoffgehalts während des Schichtwachstums beeinflusst werden. Durch gezielte Variation dieser Beschichtungsparameter wurden CrN‐Schichten mit den bevorzugten Kristallgitterstrukturen (111) und (200) abgeschieden, mit dem Ziel deren Abdeckungsfähigkeit von Störstellen zu untersuchen. Für die gezielte Untersuchung und Vergleichbarkeit der Ergebnisse wurden Vickerseindrücke HV 0,5 als bewusst gestaltete Störstellen auf der Grundwerkstoffoberfläche aufgebracht. Als Grundwerkstoff diente niedriglegierter Stahl (100Cr6). Die Kristallgitterorientierungen der abgeschiedenen Schichten wurden zunächst anhand von röntgenographischen Messungen (XRD) identifiziert. Anhand weiterer rasterelektronenmikroskopischer Aufnahmen (REM) wurden die bewusst erzeugten Störstellen in Form von Vickerseindrücken und Ritzspuren sichtbar gemacht, mit dem Ziel die Schichtqualität und die Mikrostruktur um Fehlstellen zu beschreiben. Imperfections on substrate surfaces can cause growth defects in hard coatings prepared by magnetron sputtering, leading to local loss of adhesion, higher friction, voids and corrosion at coating defects. CrN‐coatings are known for their high hardness and good wear resistance. In addition CrN‐coatings are better corrosion resistant than Ti based nitrides. The structure and the mechanical properties of those coatings can be influenced by varying bias voltage and gas flow during film growth. Due to variation of those parameters CrN‐coatings were deposited with preferred crystallized lattice orientations (111) and (200). The main objective of investigation is the potential to cover imperfections. Vickers indentations (HV 0.5) were applied as designed imperfections. As base material low alloyed steel was used (100Cr6). At first crystallized lattice orientations were identified by X‐ray diffraction (XRD). Further scanning electron microscope analysis (SEM) was applied to identify and study crystallized lattice orientations near those imperfections.     

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.     

Stofftransport durch Schichtsysteme aus Polymeren und dünnen anorganischen Schichten

Mass transport through layer systems consisting of polymers and thin inorganic layers Flexible layer systems from polymeric substrates, thin inorganic layers deposited by vacuum coating and additional polymeric layers are frequently in use to obtain high barrier properties, predominantly against oxygen and water vapour. Especially in cases where additional polymeric coatings are able to fill defects in the inorganic layers, barrier properties of the resulting layer systems show a stronger dependence on their thickness. For the transport of condensable substances, especially of water vapour, an additional porosity in the sub‐nm‐size can be assigned to the inorganic layers. This, however, has a negligible effect on gas permeation. Multilayer structures made from substrates and alternating polymeric and inorganic layers show much better barrier properties than single polymeric substrates coated with single inorganic layers. These improvements, however, are less than previously reported here. Moreover, also in these cases, the condensation of water vapour in sub‐nm pores gives much higher rates for the permeation of substances than expected from simple defect models.     

Keimbildung und Wachstum von TiO2 in dünnen Schichten

Nucleation and growth of TiO₂ in thin films The morphology of thin films of TiO₂ reflects the whole production process. Rutile nuclei are generated by bombardment of the growing film with particles with an energy of about 100 eV, presumably by subplantation. Anatase grows faster in amorphous films, due to lower mechanical stress. Evaporated films are metastable at room temperature and can get reproducible optical properties by postheating at the deposition temperature. The increase of the refractive index with increasing mass density cannot be described with a ClausiusMosotti approach, due to the inhomogeneous structure of the films.     

Eine neue Methode zur Festigkeits- und Zähigkeitsbestimmung von dünnen Schichten

A New Method of Determining Strength and Fracture Toughness of Thin Films A method is presented for measuring strength and fracture toughness of thin films. The basic idea of this method is to use a compact steel specimen as a substrate, which is deeply precracked by means of fatigue loading prior to the coating process. Under bend loading of this composite crack opening occurs accompanied by straining the free-standing thin film which bridges the crack. Film rupture firstly occurs at the front face of the specimen followed by crack growth on both sides. The film properties can be derived by eliminating the substrate effect through determining the difference between the two load-displacement curves corresponding to the intact and the damaged film, respectively. The strength of the film can be calculated from the load difference at film rupture at the front face of the composite. The fracture toughness is evaluated from load and compliance change during successive crack growth on both sides of the specimen. First results on PACVD TiN-films are presented and compared with available bulk data, thus demonstrating the applicability of the proposed method.     

Steuerung der Benetzungseigenschaften von optisch transparenten Polymeren durch Antireflexstrukturen und dünne Schichten

Controlled wetting of optical polymers by antireflective structures and thin films The wetting behaviour of antireflective structures can be modified by additional coatings to become superhydrophobic or hydrophilic. The sub‐wavelength structures which increase the samples transmission are generated by plasma etching. Bump structures with large aspect ratio show a Lotus‐like behaviour immediately after coating with a thin hydrophobic layer. In case of PMMA the Lotus‐state can only be achieved if a thin silica layer is arranged below the hydrophobic top‐layer.     

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.     

Optisch dünne Schichten aus Sicht eines Anwenders

Optical thin films are used for example, in precision optics. Their effect is important for lenses with many elements. In special plants, materials are evaporated in order to deposit to a thin film on substrates. Cleaning before and smoothing after deposition are also steps in thin film production. Because of its advantages, ion-assisted deposition of cold substrates overcomes conventional physical vapour deposition of heated substrates.     

Der Nachweis dünner Fremdschichten auf Kontaktoberflächen

The detection of thin contaminated layers on contact surfaces . Today electrical contacts must satisfy requirements which are growing steadily. The detection of very thin contaminated layers at contact surfaces therefore becomes very important. Clad gold contacts were contaminated with very small amounts of Zink. Contact resistance measurements and surface analysis measurements by AES and SIMS were shown to be adequate for the detection of this surface contamination.