Steffen Drache

Plasma diagnostics of low pressure high power impulse magnetron sputtering assisted by electron cyclotron wave resonance plasma

This paper reports on an investigation of the hybrid pulsed sputtering source based on the combination of electron cyclotron wave resonance (ECWR) inductively coupled plasma and high power impulse magnetron sputtering (HiPIMS) of a Ti target. The plasma source, operated in an Ar atmosphere at a very low pressure of 0.03 Pa, provides plasma where the major fraction of sputtered particles is ionized. It was found that ECWR assistance increases the electron temperature during the HiPIMS pulse. The discharge current and electron density can achieve their stable maximum 10 μs after the onset of the HiPIMS pulse. Further, a high concentration of double charged Ti++ with energies of up to 160 eV was detected. All of these facts were verified experimentally by time-resolved emission spectroscopy, retarding field analyzer measurement, Langmuir probe, and energy-resolved mass spectrometry.

Investigation of ionized metal flux in enhanced high power impulse magnetron sputtering discharges

The metal ionized flux fraction and production of double charged metal ions Me2+ of different materials (Al, Cu, Fe, Ti) by High Power Impulse Magnetron Sputtering (HiPIMS) operated with and without a pre-ionization assistance is compared in the paper. The Electron Cyclotron Wave Resonance (ECWR) discharge was employed as the pre-ionization agent providing a seed of charge in the idle time of HiPIMS pulses. A modified grid-free biased quartz crystal microbalance was used to estimate the metal ionized flux fraction ξ. The energy-resolved mass spectrometry served as a complementary method to distinguish particular ion contributions to the total ionized flux onto the substrate. The ratio between densities of doubly Me2+ and singly Me+ charged metal ions was determined. It is shown that ECWR assistance enhances Me2+ production with respect of absorbed rf-power. The ECWR discharge also increases the metal ionized flux fraction of about 30% especially in the region of lower pressures. Further, the suppression o...

Study of mass and cluster flux in a pulsed gas system with enhanced nanoparticle aggregation

The paper is focused on investigation of enhanced metal (Cu) cluster growth in a source of Haberlands type using pulsed gas aggregation. The aggregation Ar gas was delivered into the cluster source in a pulse regime, which results in the formation of well pronounced aggregation pressure peaks. The pressure peaks were varied by varying the different pulse gas frequency at the same mean pressure kept for all experiments. Hence, we were able to study the effect of enhanced aggregation pressure on cluster formation. Time-resolved measurements of cluster mass distribution were performed to estimate the mass and particle flux. The paper demonstrates that pulse gas aggregation influences growth of Cu nanoparticles, i.e., cluster mass/size, mass flux, and particle flux emitted from the cluster source. It was found that cluster mass related quantities are strongly influenced by pulsed gas frequency; the highest value of mass flux appears at the most pronounced pressure peaks. On the other hand, the particle flux depends only slightly on the gas pulse frequency. The explanation based on cooling and thermalization of sputtered particles is discussed in the paper.

DC Operated Air Plasma Jet for Antimicrobial Copper Coatings on Temperature Labile Surfaces

Atmospheric pressure plasmas are an appealing alternative for surface treatments. An advantage offered by nonthermal plasmas in particular is the modification of temperature sensitive materials. Here, we present copper coatings on acrylonitrile butadiene styrene that were achieved with a nonthermal dc operated air plasma jet.

Effects of reactive oxygen species on single polycation layers.

Positively charged, branched polyethylenimine (PEI) adsorbed onto silicon wafers and silica surfaces are attacked by free hydroxyl radicals. With AFM colloid probe technique, the surface forces between PEI layers are measured. Force profiles show that an electrostatic repulsion dominates the surface forces between freshly deposited PEI layers. After radical attack, both surface potential and surface charge density are reduced by a factor of about 0.5, while the Debye length remains unchanged. Adsorbed gold nanoparticles and force volume measurements show a homogeneous distribution of the surface charge on length scales between 40 nm and 30 μm. For radical attacked PEI layers, we find a 10% decrease of saturation coverage of gold nanoparticles. This is consistent with the decreased surface charge density, if the electrostatic three-body interaction is taken into account. Nevertheless, the NP adsorption kinetics are slowed down suggesting that the PEI layer is inhomogeneous on the nm-scale after radical attack.

Dynamic Study of Dual High-Power Impulse Magnetron Sputtering Discharge by Optical Emission Imaging

Fast optical emission imaging was employed for dynamic study of dual-high-power impulse magnetron sputtering discharge. The sputtering sources were equipped with reversed polarity of magnets, i.e., so-called closed magnetic field between magnetrons. Plasma is confined in closed magnetic field between targets alternately employed as cathode/anode. This type of magnetic confinement affects the transport of electrons and also the ionization processes of neutral particles present in the plasma, as will be shown in this paper.

Antimicrobial copper-coatings on temperature labile surfaces deposited with a DC plasma jet operated with air

Summary form only given. Non-thermal plasma jets are currently investigated for applications in plasma medicine. We have investigated the potential of a plasma jet that was originally developed for medical applications. The jet is generated by flowing air through the discharge channel of a microhollow cathode geometry. The temperature of the plasma itself can reach values well above 1000°C but the gas flow is effectively cooling down the expelled afterglow plume to temperatures of about 40°C within a distance of 10-15 mm. We deposited copper on silicon and AcrylnitrilButadien-Styrene (ABS). Respective substrates were placed at a distance of 10 mm and moved through the jet in a meander pattern, covering an area of 2 cm by 2 cm. For an exposure time of 864 s we found a similar distribution of copper deposits for both materials. Individual islets had a size in the range of 50400 nm and interspatial distances of 100-500 nm. SEM images show some distinct differences for coatings on silicon and ABS. In particular smaller deposits on silicon appear crystalline. Conversely, the fringes of deposits on ABS seem to merge with the substrate. XPS-measurements show that the amount of copper deposited scales with operating parameters up to a certain point. The dimensions of the deposition patterns are much smaller than the size of most bacteria. The anticipated antimicrobial effect was confirmed for ABS by an observed reduction of 95% in bacterial growth of Staphylococcus aureus when comparing coated and uncoated samples.