Publications by Alan Howling | EPFL Graph Search

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A large area antenna generates a plasma by both inductive and capacitive coupling; it is an electromagnetically coupled plasma source. In this work, experiments on a large area planar RF antenna source are interpreted in terms of a multi-conductor transmis ...

Surface dielectric barrier discharge performance deteriorates in humid air, with permanent and/or reversible degradation of its components. Plasma operation in a humid environment is unavoidable when humid air or water-containing materials are treated. Exp ...

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 ...

Plasma diagnostics for large area, industrial RF parallel-plate reactors can be useful for process optimization and monitoring, provided that their implementation is practical and non-intrusive. For instance, Fourier transform infrared (FTIR) absorption sp ...

The optimal plasma parameters for plasma processing, such as deposition of microcrystalline silicon from silane and hydrogen, are generally chosen in steady-state discharge conditions. However, this steady state must be reached in a short time after plasma ...

In situ Fourier transform infrared (FTIR) absorption spectroscopy has been used to determine the fractional depletion of silane in a radio-frequency (ri) glow discharge. The technique used a simple single-pass arrangement and was implemented in a large-area industrial reactor for deposition of amorphous silicon. Measurements were made on silane plasmas for a range of excitation frequencies. It was observed that, at constant plasma power, the fractional depletion increased from 35% at 13.56 MHz to 70% at 70

A helicon-based plasma source is under development and exploration at CEA-IRFM to produce an efficient and dense magnetized plasma column. The final objective of this development is the extraction and acceleration of a blade-like negative ion beam in view ...

Particle contamination formed in reactive plasmas imposes an upper limit on the rate for particle-free deposition. Conversely, these plasmas could be exploited to produce nanometric clusters and particles for various applications. Infrared absorption spectroscopy has been applied to analyse the chemical composition of suspended particles. Mass spectrometry was also used to investigate cluster formation in these deposition plasmas. In pure silane plasmas, a random model reproduces the measured mass spectra,

The evolution of the argon metastable states density has been studied by absorption spectroscopy in power-modulated plasmas of argon and a mixture of 4% silane in argon. A small concentration of silane suppresses the argon metastable states density by molecular quenching. This molecular quenching adds to the electronic collisional dissociation to increase the silane dissociation rate as compared with pure silane plasmas. Using time-resolved emission spectroscopy, the role of metastable states in excitation

Non-uniform voltage distribution across the electrode area results in inhomogeneous thin-film RF plasma deposition in large-area reactors. In this work, a two-dimensional analytic model for the calculation of the voltage distribution across the electrode area is presented. The results of this model are in good agreement with measurements performed without plasma at 13.56 MHz and 70 MHz in a large-area reactor. The principal voltage inhomogeneities are caused by logarithmic singularities in the vicinity of R

The electromagnetic standing wave effect can become the main source of nonuniformity limiting the use of very high frequency in large area reactors exceeding 1 m(2) required for industrial applications. Recently, it has been proposed and shown experimental ...

Experiments using a lens-shaped circular electrode are described to measure the correction of plasma nonuniformity due to the standing wave effect in a large area very high frequency plasma reactor. This work is the experimental verification of the theoretical reactor design in cylindrical geometry recently presented by L. Sansonnens and J. Schmitt, Appl. Phys. Lett. 82, 182 (2003). It is found that the lens-shaped electrode effectively compensates the standing wave effects by creating a uniform rf vertical

Particulate contamination produced during plasma-assisted deposition of amorphous silicon devices can be responsible for reduced quality and yield. The threshold for powder formation imposes an upper limit on the radio frequency (rf) power and hence the deposition rate. In this work, the parallel-plate capacitor discharge volume is illuminated and global, spatio-temporal powder dynamics are recorded by CCD camera for analysis. The onset of powder production is determined visually and from observed modificat

The frequency dependence (13.56-70 MHz) of the ion energy distribution at the ground electrode was measured by mass spectrometry in a symmetrical capacitive impedance at very high frequency allows high levels of plasma power and substrate ion flux while maintaining low levels of ion energy and electrode voltage. The lower limit of ion bombardment energy is fixed by the sheath floating potential at high frequency, in contrast to low frequencies where only the radio frequency voltage amplitude is a determinan

Using the Lambert function, Guittienne et al. [Phys. Plasmas 25, 093519 (2018)] derived two-fluid solutions for radial Langmuir probes in collisionless and isothermal plasma. In this Brief Communication, we point out the close analogy with classical compre ...

Cavity Ring Down Spectroscopy (CRDS) is used to measure the D- absolute density produced in the helicon plasma reactor RAID (Resonant Antenna Ion Device) at the Swiss Plasma Center. The birdcage geometry of the helicon antenna produces a homogeneous, high- ...

In the next generation of fusion reactors, such as DEMO, neutral beam injectors (NBIs) of high energy (0.8-1 MeV) deuterium atom swith high wall-plug efficiency (>50%) will be required to reach burning plasma conditions and to provide a significant amount ...

Resonant antennas are increasingly employed by the plasma industry, and the theory has now developed alongside the technological applications to the extent that it is timely to document the progress in this field to aid antenna design for future novel RF p ...

Designing plasma-enhanced chemical vapour deposition (PECVD) reactors to coat large-area glass plates (similar to1 m(2)) for flat panel display or solar cell manufacturing raises challenging issues in physics and chemistry as well as mechanical, thermal, and electrical engineering, and material science. In such reactive glow discharge plasma slabs, excited at RF frequency (from 13.56 MHz up to similar to 100 MHz), the thin-film deposition uniformity is determined by the gas flow distribution, as well as the

Electromagnetic wave propagation effects can give rise to important limitations for processing uniformity in large area, radio-frequency (rf) capacitive plasma reactors. The electromagnetic wavefield solution is derived for a capacitive, high-frequency, cy ...

Alan Howling

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Electromagnetic, complex image model of a large area RF resonant antenna as inductive plasma source

Surface DBD degradation in humid air, and a hybrid surface-volume DBD for robust plasma operation at high humidity

Electromagnetic sources of nonuniformity in large area capacitive reactors

Non-intrusive plasma diagnostics for the deposition of large area thin film silicon

Fast equilibration of silane/hydrogen plasmas in large area RF capacitive reactors monitored by optical emission spectroscopy

Degree of dissociation measured by FTIR absorption spectroscopy applied to VHF silane plasmas

Magnetic field configurational study on a helicon-based plasma source for future neutral beam systems

Dust particle diagnostics in rf plasma deposition of silicon and silicon oxide films

The Role of Metastable Atoms in Argon-Diluted Silane Radiofrequency Plasmas

A voltage uniformity study in large-area reactors for RF plasma deposition

Application of the shaped electrode technique to a large area rectangular capacitively coupled plasma reactor to suppress standing wave nonuniformity

Improving plasma uniformity using lens-shaped electrodes in a large area very high frequency reactor

Powder Dynamics in Very High-Frequency Silane Plasmas

Sheath impedance effects in very high frequency plasma experiments

Two-fluid plasma model for radial Langmuir probes as a converging nozzle with sonic choked flow, and sonic passage to supersonic flow

Cavity ring-down spectroscopy to measure negative ion density in a helicon plasma source for fusion neutral beams

Helicon wave-generated plasmas for negative ion beams for fusion

Resonant network antennas for radio-frequency plasma sources: Theory, technology and applications

The physics of plasma-enhanced chemical vapour deposition for large-area coating: industrial application to flat panel displays and solar cells

Electromagnetic field nonuniformities in large area, high-frequency capacitive plasma reactors, including electrode asymmetry effects