Materials and Surfaces
Today plasmas are indispensable tools in the field of thin-film technology. They create new surface properties and enable synthesis of nano-scale materials. The spectrum of plasma-assisted and ion-assisted surface treatment processes ranges from structured material removal, such as etching or precision cleaning, to modification of the interfacial properties, e.g. for control of gluability or printability, and extends to production of functional films with applications for protection against corrosion, heat or mechanical abrasion, and for the coating of optics. Synthesis of nanostructured materials or nanoparticles using plasma processes opens up new perspectives in the area of storage and transformation of renewable energy sources, such as components for electro-catalysis (battery and fuel cell technology) or hydrogen technology. The variety of applications is based on a number of engineering advantages offered by plasma processes, such as a low thermal load of components, comparative environmental compatibility, precise control, along with negligible impact on the properties of the base material. In the research programme, innovative plasma processes are studied, technical plasmas are applied, experimentally characterized, simulated and considered in context with film and surface properties. Knowledge of this correlation ultimately results in better controlled manufacturing processes, which in turn leads to superior products.
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Plasma processes can be used in the production of essential components and materials for energy storage/ conversions, such as the synthesis of catalytic surfaces in hydrogen technologies or for batteries and in related areas such as sensor technology, chemical synthesis and water and gas purification and treatment processes.
The expertise in this research program is on plasma-based synthesis methods for the deposition of nanodimensional metallic, metal-oxide and graphitic particles and thin films and their characterization. PVD (Physical Vapour Deposition) is used as plasma method, e.g., Magnetron sputtering and plasma ion assisted deposition, plasma pyrolysis and PECVD (Plasma Enhanced Chemical Vapour Deposition) and combinations of these methods to more complex hybrid methods. In addition to these vacuum-based methods, atmospheric plasma processes are also used in liquids for the generation of carbon nanostructures and metal-oxide, as well as metallic nanoparticles. Some application-oriented projects are currently being carried out, for example, in the development of synthesis methods for platinum- and nickel-based catalysts, graphene and metal-oxide-based electrode and membrane components, as well as the plasma-chemical bonding of catalysts to substrates.
Thin layers give many materials better properties. Depending on the application, the coatings fulfill special functions: with tribologically stressed components, they reduce mechanical abrasion; or with metals, the tendency to corrosion. They serve to improve the adhesion of material composites, have a decorative character, facilitate cleaning ('easy-to-clean') or can provide the plastic surfaces with increased scratch protection. As a structure-compliant, low-pore and transparent barrier layer, they prevent the permeation of gases, e.g., in PET (polyethylene terephthalate) bottles or protect sensitive goods from the diffusion of solvents ('leachables') from the walls of plastic containers. In semiconductor technology and optics, coatings function such as a dielectric, EMC shielding, and anti-reflective coatings.
In addition to plasma-assisted vacuum coating processes, the research focus is on the production of coatings using atmospheric pressure PECVD. For this purpose, non-thermal high-frequency plasma jets with plasma diagnostic methods, such as Laser-Schlieren-Deflectometry are investigated, discharge- and layer-formation models are created and interpreted, in connection with the obtained layer properties.
Plasma and ion processes are used in the manufacturing of precision optics, which are the key components for equipment in the areas of telecommunications, imaging, laser applications or measurement technology. Thus, the functional principle of many optical components, such as highly-reflective dielectric laser mirrors and high-quality optical filters is based on interference layer systems that are grown on the optical elements.
Typically, stacks of up to several hundred single layers of various materials (oxides, fluorides) each with a layer thickness of a few tens of nm are deposited. Moreover, the optical properties can also be influenced through nanoscale surface structuring, for example to generate anti-reflective coatings. To achieve the high fabrication quality of the coating systems regarding reproducibility of the coating properties (refractive index, absorption, layer thickness), the deposition process needs to be controlled. Consequently, at the INP, the properties of these coating plasmas are monitored on industrial production devices. The data are complemented by discharge models and correlated with the resulting coating properties.
The project aims to develop a resource-efficient process for the manufacturing of Oxo products, an important and economically significant class of platform chemicals e.g., fragrances and plasticizers. This should be made possible by the use of heterogeneous catalyst systems. The overall scientific objective is a novel catalysis concept, combining the advantages of homogeneous catalysis with those of heterogeneous catalysis. The following topics are examined in the INP: Variable production of functionalized organic and inorganic carrier materials by targeted plasma treatment, fixation of homogeneous catalysts on these heterogeneous surfaces, screening in various hydroformylation reactions, analytical and theoretical penetration of the interplay between catalyst preparation and catalyst properties and optimization based thereon, upscaling of the catalysis for the production of fine and bulk chemicals.
Dr. Volker Brüser
Phone: +49 3834 554 3808
Fiber-based high-performance lasers are used for processes such as welding, cutting, and drilling, as well as for surgical procedures. The material basis of these lasers is optical fibers made of doped quartz glass. This doping significantly determines their optical properties. Now a new approach is being pursued together with partners from the Leibniz Institute of Photonic Technology Jena (IPHT) in the Leibniz Competition project launched in 2017: Microwave generated plasmas achieves the required material separation under normal pressure conditions. The advantage of plasma-assisted processes lies in the fact that different parameters can be precisely adjusted when generating the doping, meaning, fibers of thus far unique quality can be produced. In INP, plasma diagnostic methods are used and supplemented by simulations and modeling methods to understand in detail the chemical and physical processes taking place in the plasma. The optimal process conditions determined in this way form the basis for the production of new glass materials at the IPHT in Jena. At the fiber drawing tower there, optical fibers are created from these fibers, whose optical properties and laser efficiency ultimately represent the benchmarks for the project.
Dr. Rüdiger Foest
Phone: +49 3834 - 554 3835
Plasma ion-assisted deposition (PIAD) is one of the established deposition processes used for production of high-quality thin film optics in laser applications, telecommunication or measurement technology. Currently in-situ monitoring for process control is limited to determining the optical thickness. However, the determination of the crucial plasma parameters is still missing. As part of the BMBF project "Plasma and Optical Technologies" (PluTO+) the INP is involved with plasma diagnostics in an industrial PIAD production plant with magnetic field-assisted DC discharge as plasma source (APS). Thus, for coating processes (TiO2, SiO2, Al2O3 and MgF2) for the first time quantitative information concerning the plasma is obtained. The data are complemented with models and correlated with the resulting layer properties. These findings permit a new quality of control algorithms that are based on the plasma parameters that are governing the film growth. Further development of PIAD processes results in better compliance with industrial specifications, such as reproducibility, spatial homogeneity, improved energy efficiency, and increased deposition rate without loss of quality.
Dr. Rüdiger Foest
Tel.: +49 3834 554 3835
Industrial box coater for production of thin-film optics
Project: Non-thermal, Reactive Atmospheric Pressure Plasma Jet
In the project of SFB/TR24 "Fundamentals of Complex Plasmas", the properties of the plasma of a non-thermal plasma jet operating under normal pressure are experimentally characterized using spectroscopic methods, described via a hybrid model, and considered in relation to the properties of deposited SiOx films. Normal pressure plasmas are highly non-stationary plasmas that can exhibit an erratic, as well as periodic, structured character. In particular the structured discharges show a potential for improved controllability of the film properties. For example, functional films based on silicon can promote adhesion, serve as a permeation barrier, enhance the scratch resistance or protect metallic surfaces from corrosion. Plasma processes under normal pressure potentially save investment costs and allow the local coating also of larger sample geometries.
Dr. Rüdiger Foest
Phone: +49 3834 - 554 3835