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.
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.
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
Schäfer, J.; Bonaventura, Z.; Foest, R.:
On the fundamental relation of laser schlieren deflectometry for temperature measurements in filamentary plasmas
Eur. Phys. J. Appl. Phys. 71 (2015), p. 20804
Peglow, S.; Pohl, M.-M.; Kruth, A.; Brüser, V.:
Plasma Based Synthesis, Electron Microscopy, and Optical Characterization of Au-, Ag-, and Ag/Au-Core-Shell Nanoparticles
J. Phys. Chem. C 119 (2015), p. 563-572
Harhausen, J.; Loffhagen, D.; Foest, R.:
Interpretation of the optical emission of argon in the plume of the Advanced Plasma Source
J. Phys. D: Appl. Phys. 48 (2015), p. 045203
Garkas, W.; Fröhlich, M.; Weltmann, K.-D.; Leyens, C.:
Oxidation and decomposition of Ti2AIN MAX phase coating deposited on nickel-based super alloy
IN718 Mat. Sci. Forum 825-826 (2015), p. 628-635