Christoph Hollenstein

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Negative ions have been clearly identified in silane rf plasmas used for the deposition of amorphous silicon. Mass spectra were measured for monosilicon up to pentasilicon negative ion radical groups in power-modulated plasmas by means of a mass spectrometer mounted just outside the glow region. Negative ions were only observed over a limited range of power modulation frequency which corresponds to particle-free plasma conditions. The importance of negative ions regarding particulate formation is demonstrat

Helicon sources are known to produce high-density plasmas and have found many applications. Different types of antenna have been used for helicon excitation but none of them generate a radio-frequency (rf) field that matches the helicon wave field determin ...

Particle formation has been investigated experimentally from the initial molecular precursors up to the final micron-sized particles in a low pressure silane rf capacitive discharge. Neutrals and ions were studied by quadrupole mass spectrometry in power-modulated plasmas: Whole series of negative ions were observed, ranging from monosilicon anions through to nanometric clusters. Anion confinement results in particles and conversely, anion de-trapping can inhibit particle formation. Plasma polymerisation is

In this work, a new type of short water vapor treatment of the interface between the p- and i-layer is presented. This novel treatment is performed under vacuum below 1 mbar for 5 min and considerably reduces the i-layer boron contamination in amorphous si ...

Medical grade poly(vinyl chloride) was modified by RF plasma-deposition of teflon-like coatings to create a platform for the physisorption of PEO-containing copolymers, Pluronics (R). Thin teflon-like coatings were deposited in an RF-plasma reactor by plas ...

Low pressure plasma spraying (LPPS) is a thermal spraying technique that has found a niche for low oxidation products. It uses a low pressure environment (i.e:, chamber pressure between 2 and 90 kPa) and yields supersonic plasma jets. The enthalpy probe te ...

This paper summarizes the results of Plasmaero (EU project) partners on the characterization of plasma actuators based on nanosecond pulsed discharges. Results cover electrical aspects, optical discharge visualizations and measurements of the plasma-induced pressure wave, this for quiescent and transonic flow regimes. Among the results, this study demonstrates that the induced pressure wave is composed of over and under pressure of1600 and -600 Pa, respectively. In transonic regime, the capability of the di

An electrostatic charge can be left on an insulating substrate after RF plasma processing, even though the plasma and surfaces are globally neutral. High voltages and breakdown can then occur when the substrate is manipulated. If the substrate is not a perfect insulator, charge appears on its back face where there is no contact with the plasma. In this case, the substrate sticks electrostatically to the electrode, and partial discharging can occur when it is lifted. Analysis of in situ charge measurements r

The oxidation behaviour of various boron-carbide samples have been studied by photoelectron spectroscopy. The exposure of sputter-cleaned surfaces to molecular oxygen at room temperature did not cause a measurable surface oxidation. An increased reactivity has been found by irradiating boron carbide with energetic oxygen ions. The highest reactivity against oxidation was obtained during the growth of a boron-carbide surface phase which revealed a marked oxygen gettering effect.

Intrinsic stress measurements were carried out on hydrogenated amorphous silicon (a-Si:H) films deposited with different excitation frequencies (13.56-70 MHz), by plasma-enhanced chemical vapor deposition. It was observed that films deposited at 70 MHz have one order of magnitude smaller intrinsic stress than those deposited at 13.56 MHz. These results have been linked to the estimated variation of the ion impact energy as a function of excitation frequency, deduced from the measured variation of the peak-t

Measurements of anions and cations are reported for hydrocarbon and silane radio frequency capacitive glow discharges. Series of anions were observed by quadrupole mass spectrometry using power-modulated plasmas, and their structures are interpreted from the form of the mass spectra. Various experiments in silane plasmas show that anion confinement results in particles and conversely, anion detrapping can inhibit particle formation. In contrast, the polymerized neutral flux magnitudes, mass spectra and dyna

The application of nanosecond pulse-driven surface dielectric barrier discharge (DBD) actuators as control devices on airfoils and turbomachinery blades in transonic flow is investigated experimentally. Images acquired with a short-exposure ICCD camera document the spatial-temporal discharge development in both absence and presence of flow, as a means of examining the effect of the ow on the actuator. In order to visualize the interaction of the DBD actuator with the ow, Schlieren images were acquired. Furt

The plasma produced by a nano pulsed surface dielectric barrier discharge (SDBD) is investigated experimentally by means of time-resolved optical emission spectroscopy. The relative populations of the most intense radiating species is determined with an in-house code for emission spectroscopy. The possibility to use low-lying states such as N2(B) and argon (2p) to characterize kinetic processes in the plasma at low electric field is demonstrated.

Contamination due to particles generated and suspended in silane rf plasmas is investigated. Powder is rendered visible by illumination of the reactor volume. This simple diagnostic for global, spatio-temporal powder dynamics is used to study particle formation, trapping, and powder reduction by power modulation.

In large-area radio-frequency (rf) capacitive reactors, the redistribution of rf current to maintain current continuity near asymmetric sidewalls causes a perturbation in rf plasma potential to propagate along the resistive plasma between capacitive sheath ...

In large area reactors, a local asymmetry of the electrode area, due to lateral grounded walls, causes a perturbation in rf plasma potential, due to the redistribution of lateral rf current, which propagates along the resistive plasma between capacitive sh ...

Dielectric barrier discharges (DBDs) are investigated in helium and nitrogen as a function of pressure from 5 to 1000 mbar. Different regimes are observed: glow, Townsend, multi-peak and filamentary, depending on pressure, power and electrode gap. In heliu ...

Dielectric Barrier Discharge in air at atmospheric pressure

A detailed study of the interaction between high-speed gas flows and surface dielectric barrier discharges (DBD) is presented. In the present paper, it is demonstrated that a DBD can be sustained in transonic airflows, up to isentropic Mach numbers of 1.1. ...

Christoph Hollenstein

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Negative-Ion Mass-Spectra and Particulate Formation in Radio-Frequency Silane Plasma Deposition Experiments

Towards an optimal antenna for helicon waves excitation

From molecules to particles in silane plasmas

High Efficiency p-i-n a-Si:H Solar Cells with Low Boron Cross-Contamination Prepared in a Large Area Single-Chamber PECVD Reactor

Fluoropolymer coating of medical grade poly(vinyl chloride) by plasma-enhanced chemical vapor deposition techniques

Inclusion of aerodynamic non-equilibrium effects in supersonic plasma jet enthalpy probe measurements

Nanosecond Pulsed Plasma Actuators

Mechanism of substrate charging after plasma processing

Oxidation Behavior of Boron-Carbide

Dependence of Intrinsic Stress in Hydrogenated Amorphous-Silicon on Excitation-Frequency in a Plasma-Enhanced Chemical Vapor-Deposition Process

Anionic clusters in dusty hydrocarbon and silane plasmas

Interaction Between Nanosecond Pulse DBD Actuators and Transonic Flow

Characterization of Kinetic Processes in Nano Pulsed SDBD

Direct Visual Observation of Powder Dynamics in Rf Plasma-Assisted Deposition

Probe measurements of plasma potential nonuniformity due to edge asymmetry in large-area radio-frequency reactors: the telegraph effect

Measurements and consequences of nonuniform radio frequency plasma potential due to surface asymmetry in large area radio frequency capacitive reactors

Atmospheric and sub-atmospheric dielectric barrier discharges in helium and nitrogen

Electron temperature measurements using N2 and Argon transitions in an ATP fast pulsed DBD

Effects of a surface dielectric barrier discharge on transonic flows around an airfoil

Effects of high-speed airflows on a surface dielectric barrier discharge