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Group High Performance Thin Film Composites: Research Areas

 

The group High Performance Thin Film Composites works on the development, characterisation and modelling of innovative thin film materials for engineering applications in manufacturing, automotive and aircraft industries, process technology, energy and in the biomedical area. The novel nanoscale thin film materials exhibit tailored multifunctional property profiles. They address societal and economically relevant topics such as environmentally friendly technologies, energy saving in industrial processes and wear protection.

The material development is based on fundamental principles of materials selection from the various classes of hard materials with metallic, covalent or ionic bonds, on the use of specific design concepts of the thin film materials on the atomic level, on the modelling of material systems, of the kinetic of gas phase deposition and of the thin films growth processes. Our focus of research is on the scientific elaboration of the correlation between growth, constitution and microstructure, and the properties and performance of the new thin film materials. In addition to the fundamental material synthesis on the laboratory scale, complex processes for the upscaling and deposition of thin film materials on an industrial deposition equipment are developed, in order to enable the coating of tools and of 3-dimensional parts and components. In order to realise this objective, various technologies of physical vapour deposition (d.c. and r.f. magnetron sputtering, cathodic arc evaporation) as well as new plasma-assisted PVD-CVD hybrid processes are used. New deposition technologies are also under development, e.g., an innovative plasma beam source for high rate deposition of carbon-based nanostructured composite thin films.

principle             

Principle arrangement for the experimental realisation of a combinatorial thin film development process by magnetron sputtering 

         

Segmented Sputtering Target

 

 

     
Transmission electron microscopy of TiC/a-C nanocomposite coatings with large TiC phase fraction       Transmission electron microscopy of TiC/a-C nanocomposite coatings with large amorphous carbon phase fraction 

 

Scale-up of synthesis processes of TiC/a-C nanocomposite coatings: sputter-targets of different compositions for industrial PVD-deposition (manufactured by Plansee Composite Materials GmbH)

Carbon based nanostructured composite thin films are one current example for the development of a new generation of wear resistant and low friction coatings. These films consist of one or more nanocrystalline hard material phases that are embedded in a matrix of amorphous carbon (a-C or a-C:X with X = N, O, H, Si). The microstructure of these materials can be modified over a wide range by adjusting the volume fractions of the crystalline and amorphous phases. This feature allows to tune mechanical properties, hardness and tribological performance in various tribo-systems of these materials in an optimum way and to design and synthesize tailor-made materials for different applications in mechanical engineering. It has been demonstrated for TiC/a-C thin films that in specific applications the amount of lubricants could be significantly reduced due to their excellent wear and friction behaviour. Such materials offer a large potential for the use in environmentally friendly technologies. 

A new research field addresses the development of novel thin film materials of transition metal oxides and transition metal oxinitrides. Ceramic thin films such as aluminium oxide (corundum) are typically brittle materials and are often difficult to synthesize in a crystalline structure by PVD methods. Following combinatorial approaches for the development of new mixed oxide thin film materials Al-Cr-O thin films with a corundum structure were successfully synthesized at a moderate process temperature of 500°C. These thin film materials exhibit properties similar to those of corundum but do simultaneously tend much less to cracking under mechanical loading. Another innovative approach to design ductile ceramic coatings is based on the incorporation of small amounts of nitrogen in such materials, in order to modify their local chemical bond situation. The synthesis of such new single-phase nanocrystalline aluminium-chromium-oxinitride thin films in corundum structure has been demonstrated.

 

     
Transmission electron microscopy of an (Al1-x,Crx)2O3 thin film in corundum structure (reactive magnetron sputter deposition, 500°C): selected area electron diffraction and identifcation of lattice planes  Transmission electron microscopy of an (Al1-x,Crx)2+δ(O1-y,Ny)3 thin film in corundum structure (reactive magnetron sputter deposition, 500°C): dark field image and selected area electron diffraction. Dense columnar structure, column diameter ca. 35 nm Suggested model of the microstructure of (Al1-x,Crx)2+δ(O1-y,Ny)3 thin films with corundum structure: nitrogen ions replace partially oxygen ion positions 

 

 

Superhard thin film materials are of fundamental interest for many technical applications. Innovative synthesis processes on laboratory and industrial scale are developed for hard amorphous carbon thin films (ta-C, DLC), cubic boron nitride (c-BN:O), boron carbide (B4C) and new hard boride-based coatings (i.e. TiB2 based thin films in the system Ti-B-C-N). By cathodic arc evaporation amorphous carbon coatings with a hardness up to 60 GPa, 10 microns thick, can be deposited. Single-phase cubic boron nitride thin films up to 2 microns thick can be synthesized by utilising a new hybrid deposition technology.

 

     
 Scanning electron microscopy cross-sectional image of an superhard amorphous carbon coating on silicon (D.C. magnetron sputtering, thickness 10 mm, hardness 50 GPa)  Scanning electron microscopy cross-sectional image of an superhard amorphous carbon coating on cemented carbide (cathodic arc evaporation, thickness 1 mm, hardness 58 GPa)  

 

 

 

Scanning electron microscopy cross-sectional image of a 2 µm thick, oxygen containing, superhard, cubic boron nitride coating with nucleation and adhesion layer on silicon substrate

Dependence of the content of cubic boron nitride and compressive stress on the d.c. substrate bias of magnetron sputtered boron nitride coatings. The ion energy is proportional to the sum of the plasma potential and the absolute value of the substrate bias. The compressive stresses can be drastically reduced by incorporation of 4.6 at.-% oxygen and post annealing.

 

 

 

 

Scanning electron microscopy cross-sectional image of a TiN/ZrN multilayer coating exhibiting 20 individual layers (dark contrast: TiN, bright contrast: ZrN)

Concept of a high performance plasma source with double-walled, water cooled parabolic reactor and micro wave antenna in its focus. Growth rates of amorphous hydrogenated carbon coatings up to 36 µm/h can be obtained.