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a-Si:H films were prepared using pure silane in the temperature range from 200 degrees C up to 400 degrees C by the very high frequency glow discharge (VHF-GD) technique. During deposition a He/Ne laser beam directed across the discharge monitored powder formation. H-content and microstructure were determined by IR-spectroscopy. The impurity contents of oxygen (O), nitrogen (N) and carbon (C) were analysed by SIMS. A surface profiler was used to measure the internal stress and thickness of the films. The sa

Stable negative ions containing up to sixteen silicon atoms have been measured by mass spectrometry in RF power-modulated silane plasmas for amorphous silicon deposition. These hydrogenated silicon cluster ions reach much higher masses than the positive ions, which have no more than six silicon atoms. This supports the view that negative ions are the precursors to particulate formation in silane plasmas. The time-dependent fluxes of positive and negative ions from the plasma are shown with a 5 mus time reso

It is now generally recognized that the excitation frequency is an important parameter in radio-frequency (rf) plasma-assisted deposition. Very-high-frequency (VHF) silane plasmas (50-100 MHz) have been shown to produce high quality amorphous silicon films up to 20 angstrom/s [H. Curtins, N. Wyrsch, M. Favre, and A. V. Shah, Plasma Chem. Plasma Processing 7, 267 (1987)], and therefore the aim of this work is to compare the VHF range with the 13.56 MHz industrial frequency in the same reactor. The principal

Microcrystalline hydrogenated silicon films (muc-Si:H) have been deposited by a high current DC plasma in argon-silane-hydrogen mixtures at growth rates up to 10 nm/s and at substrate temperatures below 500 degreesC. Scanning electron microscopy, X-ray diffraction and FTIR analyses show that these films are highly crystallized. The surface morphology depends strongly on the experimental conditions and varies from a cauliflower structure to a prismatic one. The crystalline orientation of the films also chang

Cost reduction constraints for microcrystalline silicon thin film photovoltaic solar cells require high deposition rates and high silane gas utilization efficiencies. If the requirements in deposition rate have sometimes been fulfilled, it is generally not ...

Charge-exchange collisions and radio frequency (RF) excitation combine to give peaks in the ion energy distribution measured at the ground electrode of an argon plasma in a capacitive reactor. These peaks are used as a diagnostic to reconstruct the profile of the time-averaged potential in the sheath. Particle-in-cell (PIC) simulations show that the method is accurate. The method is applied to investigate the sheath thickness as a function of excitation frequency at constant plasma power. The time-averaged

Previous measurements of SixHm- anions and electrons in the afterglow of silane discharges are analyzed here. A model of plasma anion chemistry includes two sources of anions, two possible causes of x-->x+1 anion growth, and anion loss by mutual neutralization. Comparison to pulsed-discharge measurements for x=1-6, for a range of discharge times, clearly establishes radical reactions as the primary cause of anion growth; prior estimates generally suggested silane reactions. This comparison also indicates th

Partial-depth modulation of the rf power in a capacitive discharge is used to investigate the relative importance of negative ions and neutral radicals for particle formation in low-power low-pressure silane plasmas. For less than 85% modulation depth, anions are trapped indefinitely in the plasma and particle formation ensues, whereas the polymerized neutral flux magnitudes and dynamics are independent of the modulation depth and the powder formation. These observations suggest that negative ions could be

Understanding particle dynamics requires comparison of spatially resolved measurements with two-dimensional (2-D) simulations, In this work, a cross section of a capacitive discharge is illuminated with an expanded laser beam, and global scattered light is recorded by camera, Plasma equipotentials are visualized using the scattered intensity from a small amount of particles trapped in an argon plasma. At low RF voltages, good agreement is found with 2-D fluid simulations, whereas displacement of the power c

A simple one-dimensional model for plasma deposition in a rectangular showerhead reactor with single side pumping has been developed in order to explain the mechanisms which yield uniform deposition using this gas flow configuration. Although the flow velocity increases linearly with distance towards the pumping side, the solution of the transport equations for the neutral species shows that their number densities are constant throughout the reactor. Consequently, the plasma and surface deposition reactions

Plasma treatments are currently being assessed as a seed processing technology for agricultural purposes. There is sufficient information as a proof-of-concept, but a lack of standardization in the methodology prevents a convincing evaluation of plasma tre ...

The cavity ring-down technique is applied to an industrial-scale radio-frequency (rf) plasma reactor for the measurement of the density and spatial profile of negative ions in pure oxygen and hydrogen rf plasmas, and for the detection of nanometric particles in argon-silane plasmas. The real-time observation of powder formation is demonstrated to be feasible by the cavity ring-down technique. An observed plasma-induced spurious drift of the ring-down time is also studied and related to water desorption from

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

Heat-resistant spores on a dry, heat- and water-sensitive food matrix are difficult to inactivate. Radioactive or X-ray exposure is allowed and accepted only for some selected commodities. Non-thermal atmospheric pressure plasma treatments could offer an e ...

As a new concept of Neutral Beam Injectors (NBI) for DEMO-like reactors, SIPHORE (IRFM, CEA, in France) expects to extract negative deuterium ions and photo-neutralize the accelerated D-. The Swiss Plasma Center (SPC) of EPFL is involved in this project by ...

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

We study experimentally the longitudinal and transverse wakefields driven by a highly relativistic proton bunch during self-modulation in plasma. We show that the wakefields' growth and amplitude increase with increasing seed amplitude as well as with the ...

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 ...

Current agricultural practices are not sustainable; however, the non-thermal plasma treatment of seeds may be an eco-friendly alternative to alter macroscopic plant growth parameters. Despite numerous successful results of plasma-seed treatments reported i ...

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

Alan Howling

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Influence of Higher Deposition Temperature on a-Si-H Material Properties, Powder Formation and Light-Induced Degradation, Using the Vhf (70 Mhz) Glow-Discharge Technique

Negative Hydrogenated Silicon Ion Clusters as Particle Precursors in RF Silane Plasma Deposition Experiments

Frequency-Effects in Silane Plasmas for Plasma Enhanced Chemical Vapor-Deposition

Rapid deposition of hydrogenated microcrystalline silicon by a high current DC discharge

Optimization of the microcrystalline silicon deposition efficiency

Reconstruction of the Time-Averaged Sheath Potential Profile in an Argon Radiofrequency Plasma Using the Ion Energy-Distribution

Anion reactions in silane plasma

Partial-depth modulation study of anions and neutrals in low-pressure silane plasmas

Global visualization of powder trapping in capacitive RF plasmas by two-dimensional laser scattering

A gas flow uniformity study in large-area showerhead reactors for RF plasma deposition

Entering the plasma agriculture field: An attempt to standardize protocols for plasma treatment of seeds

Applications of the cavity ring-down technique to a large-area rf-plasma reactor

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

Cold Atmospheric Plasma Inactivation of Microbial Spores Compared on Reference Surfaces and Powder Particles

First B-dot measurements in the RAID device, an alternative negative ion source for DEMO neutral beams

From molecules to particles in silane plasmas

Experimental study of wakefields driven by a self-modulating proton bunch in plasma

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

An In Situ FTIR Study of DBD Plasma Parameters for Accelerated Germination of Arabidopsis thaliana Seeds

Mechanism of substrate charging after plasma processing