Christoph Hollenstein

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Plasma conditions for microcrystalline silicon deposition generally require a high flux of atomic hydrogen, relative to SiH alpha=0 -> 3 radicals, on the growing film. The necessary dominant partial pressure of hydrogen in the plasma is conventionally obta ...

Experimental investigations and numerical modeling with the objective to study the effects that surface discharge plasmas can provoke on aerodynamic flow situations, including high speed flows present in aero-engines, are undertaken at EPFL. The actuator’s potential to influence the flow under realistic flight and engine operating conditions, largely depends on its geometric configuration and the power supply. Initially, a long-life (more than 12 hours) surface discharge actuator was designed at EPFL and pr

One of the main challenges for silicon thin film deposition for solar cell applications is to achieve high rate deposition in order to reduce the manufacturing costs. However, when silane and hydrogen are used as precursor gas in parallel plate plasma-enha ...

The time-resolved fluxes of negative polysilicon hydride ions from a power-modulated rf silane plasma have been measured by quadrupole mass spectrometry and modeled using a simple polymerization scheme. Experiments were performed with plasma parameters suitable for high-quality amorphous silicon deposition. Polysilicon hydride anions diffuse from the plasma with low energy (approximately 0.5 eV) during the afterglow after the electron density has decayed and the sheath fields have collapsed. The mass depend

Plasma created during electrical discharge machining is systematically investigated using optical emission spectroscopy. Typical spectra show a strong H-alpha and continuum radiation, with many lines emitted by impurities coming from electrode and workpiece materials. The dielectric molecules are cracked by the discharge. Changing polarity affects the electrode wear and workpiece erosion rates, which can be qualitatively seen on the spectra. Time-resolved spectroscopy shows that the plasma density reaches 2

New dedicated coating processes which are based on the well-known LPPS (TM) technology but operating at lower work pressure (100 Pa) are being actively developed. These hybrid technologies contribute to improve the efficiencies in the turbine industry such ...

In small area capacitive reactors, the rf and dc components of the plasma potential can be assumed to be uniform over all the plasma bulk because of the low plasma resistivity. In large area reactors, however, the rf plasma potential can vary over a long range across the reactor due to rf current flow and the nonzero plasma impedance. A perturbation in rf plasma potential, due to electrode edge asymmetry or the boundary of a dielectric substrate, propagates along the resistive plasma between capacitive shea

Medical-grade poly(vinyl chloride) (PVC) was chemically modified to study how the incorporation of monovalent silver influences Pseudomonas aeruginosa adhesion and colonization. The modification investigated consisted of a radio frequency-oxygen (RF-O-2) glow discharge pre-functionalization, followed by a two-step wet-treatment in sodium hydroxide and silver nitrate solutions. X-ray photoelectron spectroscopy (XPS) analysis and contact angle measurements were used to investigate the chemical nature and surf

This paper presents an investigation into radio frequency (rf) breakdown for electrodes with holes or protrusions, approximating the situation in real reactors and providing a benchmark for fluid simulations. rf breakdown curves (voltage versus pressure) g ...

To determine self-consistently the time evolution of particle size and their number density in situ multi-angle polarization-sensitive laser light scattering was used. Cross-polarization intensities (incident and scattered light intensities with opposite polarization) measured at 135 degrees and ex situ transmission electronic microscopy analysis demonstrate the existence of nonspherical agglomerates during the early phase of agglomeration. Later in the particle time development both techniques reveal spher

Hydrogenated amorphous silicon has been prepared at a plasma excitation frequency in the very-high-frequency band at 70 MHz with the glow discharge technique at substrate temperatures between 280 and 50-degrees-C. The structural properties have been studied using hydrogen evolution, elastic recoil detection analysis, and infrared spectroscopy. The films were further characterized by dark and photoconductivity and by photothermal deflection spectroscopy. With respect to films prepared at the conventional fre

Micro-particle formation in low pressure silane (SiH4) plasmas has been of technical interest and concern for at least 40 years. Negative ion plasma chemistry is a candidate for the initial nucleation, which has been extensively studied both experimentally ...

Thin, hydrogenated silicon and carbon containing films have been deposited by the siliconization procedure on targets made from some metal alloys, pure metals, graphite and Si single crystal. The deposits were investigated by electron microprobe and surface analysis techniques combined with ion sputtering, infrared spectroscopy, mass spectrometry, ellipsometry and by nuclear reaction and backscattering techniques. The stoichiometry of the layers were controlled by particle balance. They are amorphous, semit

In situ Fourier transform infrared absorption spectroscopy has been used to study the composition of particles formed and suspended in radio-frequency discharges of silane-oxygen-argon gas mixtures. The silane gas constumption was observed by infrared absorption. The stoichiometry of the produced particles depends on the silane flow rate and was compared with commercial colloidal silica. A small proportion of silane gas produces nanometric stoichiometric particles whereas a large proportion produces larger

Following the analytical description of the collisionless high-voltage capacitive RF sheath in Lieberman (1988) and of the collisional high-voltage capacitive RF sheath in Lieberman (1989), electrical sheath parameters are calculated for a square-wave ie RF discharge current. The interest in the square-wave current lies in the analytical simplicity of the solutions, The spatial dependences of the time-averaged electrostatic potential electric field (E) over bar, net-charge carrier density

The plasma created during electrical discharge machining is investigated with imaging and spatially-resolved optical emission spectroscopy. Analysis of the pre-breakdown duration shows that the breakdown is of stochastic nature. Due to the presence of gas ...

The process parameters of an inductively coupled thermal plasma used for nanopowder synthesis are experimentally investigated using various plasma diagnostics and in situ powder monitoring methods. An enthalpy probe technique is applied to characterize the ...

In situ Fourier transform infrared spectroscopy was used to study the powder formation of hexamethyldisiloxane/O-2 plasmas. The spectra show that oxygen plays an important role at the beginning of the process. A large amount of oxygen is responsible for in ...

Theory and experiment show that two electromagnetic modes are necessary and sufficient to determine the field nonuniformity within a parallel-plate rf capacitive plasma reactor. These two modes give rise to the standing wave effect and the telegraph effect ...

The fluctuating behaviour of a Sulzer Metco F4 DC plasma gun has been investigated. The time dependencies of the arc voltage and current and of the optical emission of the plasma jet have been measured. An optical fibre inside the gun allows direct measurement of optical fluctuations of the arc. Spectral and statistical analysis of the recorded signals are, presented for various working gas mixtures and for two types of gas injection. There is a dominant fluctuation frequency around 4 kHz which appears to b

Christoph Hollenstein

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Hydrogen-dominated plasma, due to silane depletion, for microcrystalline silicon deposition

Aero Engine Flow Control by Surface Discharge Plasma

Powder formation in SiH[sub 4]–H[sub 2] discharge in large area capacitively coupled reactors: A study of the combined effect of interelectrode distance and pressure

Time-Resolved Measurements of Highly Polymerized Negative-Ions in Radio-Frequency Silane Plasma Deposition Experiments

Optical emission spectroscopy of electrical discharge machining plasma

Plasma Spray-CVD: A New Thermal Spray Process to Produce Thin Films from Liquid or Gaseous Precursors

Nonuniform radio-frequency plasma potential due to edge asymmetry in large-area radio-frequency reactors

Inhibition of bacterial adhesion on PVC endotracheal tubes by RF-oxygen glow discharge, sodium hydroxide and silver nitrate treatments

Radio frequency breakdown between structured parallel plate electrodes with a millimetric gap in low pressure gases

Particle agglomeration study in rf silane plasmas: In situ study by polarization-sensitive laser light scattering

Influences of a High-Excitation Frequency (70 Mhz) in the Glow-Discharge Technique on the Process Plasma and the Properties of Hydrogenated Amorphous-Silicon

Multiple dehydrogenation reactions of negative ions in low pressure silane plasma chemistry

Properties of thin a-C/Si:H coatings applied to TEXTOR

Silicon oxide particle formation in RF plasmas investigated by infrared absorption spectroscopy and mass spectrometry

Power laws for the spatial dependence of electrical parameters in the high-voltage capacitive RF sheath

Time-resolved imaging and spatially-resolved spectroscopy of electrical discharge machining plasma

The influence of process parameters on precursor evaporation for alumina nanopowder synthesis in an inductively coupled rf thermal plasma

Influence of Argon and Nitrogen Admixture in HMDSO/O-2 Plasmas onto Powder Formation

Electromagnetic sources of nonuniformity in large area capacitive reactors

Characterisation and origin of arc fluctuations in a F4 DC plasma torch used for thermal spraying