Our competence in coating science and technology is based on a holistic approach to the fundamentals, technology and application of thin films and coatings deposited at relatively low temperatures. We determine our fields of research according to current issues of science and the needs of relevant industries. Currently, these are, for example, gas barrier coatings or porous catalyst layers for the energy sector as well as switchable layers for scientific instrumentation.
We use non-thermal energy sources such as plasmas, ion beams and photons to investigate, develop and improve deposition processes of films and coatings. Using a colaborative approach of researchers from different disciplines in chemistry, physics and engineering allows us to develop practical coating technologies for "demanding" (e.g. flexible) substrates. For this purpose, we have a wide range of vacuum and atmospheric pressure techniques in lab and technical scale available.
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Highlights
Hydrogen permeation through uniaxially strained SiOx barrier thin films photochemically prepared on PET foil substrates
P.C. With, T. Pröhl, J.W. Gerlach, A. Prager, A. Konrad, F. Arena, U. Helmstedt
Int. J. Hydrogen Energy 81 (2024) 405-410
https://doi.org/10.1016/j.ijhydene.2024.07.249Hydrogen permeation through uniaxially strained thin SiOx based gas barrier films, formed at room temperature and ambient pressure on PET foil substrates by UV photochemical conversion (Photoconversion), was investigated using a dedicated measurement system. Hydrogen permeation measurements were conducted as a function of the stack of laminated single SiOx barrier films, of the sample temperature as well as of the uniaxial mechanical strain applied to the samples. The results demonstrate a significant overall improvement of the hydrogen barrier properties for both single SiOx barrier films on PET and laminated single SiOx barrier films on PET. In the case of strained samples, the hydrogen barrier properties deteriorate due to stress-induced crack formation in the barrier films. This deterioration is strongest for strained single SiOx barrier films but can be substantially reduced by laminating single SiOx barrier films.
Glows, arcs, ohmic discharges: An electrode-centered review on discharge modes and the transitions between them
A. Anders
Appl. Phys. Rev. 11, 031310 (2024)
https://doi.org/10.1063/5.0205274Ever since they have been studied, gas discharges have been classified by their visual appearance as well as by their current and voltage levels. Glow and arc discharges are the most prominent and well-known modes of discharges involving electrodes. In a first approximation, they are distinguished by their current and voltage levels, and current–voltage characteristics are a common way to display their relations. In this review, glow discharges are defined by their individual electron emission mechanism such as secondary electron emission by photons and primary ions, and arcs by their respective collective mechanism such as thermionic or explosive electron emission. Emitted electrons are accelerated in the cathode sheath and play an important role in sustaining the discharge plasma. In some cases, however, electron emission is not important for sustaining the plasma, and consequently we have neither a glow nor an arc discharge but a third type of discharge, the ohmic discharge. In part 1 of this review, these relationships are explained for quasi-stationary discharges, culminating with updated graphical presentations of I–V characteristics (Figs. 15 and 16). In part 2, further examples are reviewed to include time-dependent discharges, discharges with electron trapping (hollow cathode, discharges) and active anode effects.
Heteroepitaxial growth of Ga2O3 thin films on Al2O3(0001) by ion beam sputter deposition
D. Kalanov, J. W. Gerlach, C. Bundesmann, J. Bauer, A. Lotnyk, H. von Wenckstern, A. Anders, Y. Unutulmazsoy
J. Appl. Phys. 136, 015302 (2024)
https://doi.org/10.1063/5.0211179Deposition of epitaxial oxide semiconductor films using physical vapor deposition methods requires a detailed understanding of the role of energetic particles to control and optimize the film properties. In the present study, Ga 2O 3 thin films are heteroepitaxially grown on Al 2O 3(0001) substrates using oxygen ion beam sputter deposition. The influence of the following relevant process parameters on the properties of the thin films is investigated: substrate temperature, oxygen background pressure, energy of primary ions, ion beam current, and sputtering geometry. The kinetic energy distributions of ions in the film-forming flux are measured using an energy-selective mass spectrometer, and the resulting films are characterized regarding crystalline structure, microstructure, surface roughness, mass density, and growth rate. The energetic impact of film-forming particles on the thin film structure is analyzed, and a noticeable decrease in crystalline quality is observed above the average energy of film-forming Ga + ions around 40 eV for the films grown at a substrate temperature of 725 °C.
Toward decoupling the effects of kinetic and potential ion energies: Ion flux dependent structural properties of thin (V,Al)N films deposited by pulsed filtered cathodic arc
Y. Unutulmazsoy, D. Kalanov, K. Oh, S. K. Aghda, J. W. Gerlach, Nils Braun, F. Munnik, A. Lotnyk, J. M. Schneider, A. Anders
J. Vac. Sci. Technol. A 41, 063106 (2023)
https://doi.org/10.1116/6.0002927Pulsed filtered cathodic arc deposition involves formation of energetic multiply charged metal ions, which help to form dense, adherent, and macroparticle-free thin films. Ions possess not only significant kinetic energy, but also potential energy primarily due to their charge, which for cathodic arc plasmas is usually greater than one. While the effects of kinetic ion energy on the growing film are well investigated, the effects of the ions’ potential energy are less known. In the present work, we make a step toward decoupling the contributions of kinetic and potential energies of ions on thin film formation. The potential energy is changed by enhancing the ion charge states via using an external magnetic field at the plasma source. The kinetic energy is adjusted by biasing the arc source (“plasma bias”), which allows us to approximately compensate the differences in kinetic energy, while the substrate and ion energy detector remain at ground. However, application of an external magnetic field also leads to an enhancement of the ion flux and hence the desired complete decoupling of the potential and kinetic energy effects will require further steps. Charge-state-resolved energy distribution functions of ions are measured at the substrate position for different arc source configurations, and thin films are deposited using exactly those configurations. Detailed characterization of the deposited thin films is performed to reveal the correlations of changes in structure with kinetic and potential energies of multiply charged ions. It is observed that the cathode composition (Al:V ratio) strongly affects the formation of the thermodynamically stable wurtzite or the metastable cubic phase. The external magnetic field applied at the arc source is found to greatly alter the plasma and, therefore, to be the primary, easily accessible “tuning knob” to enhance film crystallinity. The effect of “atomic scale heating” provided by the ions’ kinetic and potential energies on the film crystallinity is investigated, and the possibility to deposit crystalline (V,Al)N films without substrate heating is demonstrated. This study shows an approach toward distinguishing the contributions stemming from kinetic and potential energies of ions on the film growth, however, further research is needed to assess and distinguish the additional effect of ion flux intensity (current).