
Sebastian WilczekRuhr University Bochum | RUB · Department of Electrical and Information Engineering
Sebastian Wilczek
Doctor of Engineering
About
59
Publications
8,051
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
866
Citations
Introduction
Additional affiliations
September 2014 - present
Publications
Publications (59)
Surface dielectric barrier discharges (sDBD) are efficient and scalable plasma sources for plasma-based gas conversion. One prominent feature of an sDBD is the generation of an ion wind, which exerts a force on the neutrals, thus leading to an efficient mixing of plasma and a passing gas stream. This becomes apparent by the creation of upstream and...
An atmospheric pressure surface dielectric barrier discharge in helium–nitrogen mixtures is investigated experimentally using phase-resolved optical emission spectroscopy and computationally employing a two-dimensional simulation framework. A good qualitative agreement between experiments and simulations is found. It is shown that by applying micro...
Based on experiments and simulations, various plasma parameters are found to undergo a hysteresis as a function of the driving voltage amplitude in capacitively coupled CF4 discharges. Phase Resolved Optical Emission Spectroscopy reveals that the discharge operates in a hybrid combination of the drift-ambipolar and α-mode at low voltage. In this mo...
Three-dimensional (3D) etching of materials by plasmas is an ultimate challenge in microstructuring applications. A method is proposed to reach a controllable 3D structure by using masks in front of the surface in a plasma etch reactor in combination with local magnetic fields to steer the incident ions in the plasma sheath region toward the surfac...
This study investigates the flow field induced by a surface dielectric barrier discharge (SDBD) system, known for its efficient pollution remediation of volatile organic compounds (VOCs). We aim to understand the flow dynamics that contribute to the high conversion observed in similar systems using this specific SDBD design. Examining how the surfa...
Designing efficient plasma processes requires a fundamental understanding of the plasma properties and the underlying physical chemistry . Reaction kinetic (global) plasma modeling is capable of simulating complex plasma systems, without being overly computationally intensive. In this work, we focus on the excitation of electronic states in a high...
In capacitively coupled radio frequency (CCRF) discharges, the interaction of the plasma and the surface boundaries is linked to a variety of highly relevant phenomena for technological processes.
One possible plasma-surface interaction is the generation of secondary electrons (SEs), which significantly influence the discharge when accelerated in t...
This study investigates the flow field induced by a surface dielectric barrier discharge (SDBD) system, known for its efficient pollution remediation of volatile organic compounds (VOCs). We aim to understand the flow dynamics that contribute to the high conversion observed in similar systems. Experimental techniques, including schlieren imaging an...
The electron dynamics and the mechanisms of power absorption in radio-frequency (RF) driven,
magnetically enhanced capacitively coupled plasmas (MECCPs) at low pressure are investigated.
The device in focus is a geometrically asymmetric cylindrical magnetron with a radially nonuniform
magnetic field in axial direction and an electric field in radia...
In capacitively coupled radio frequency (CCRF) discharges, the interaction of the plasma and the surface boundaries is linked to a variety of highly relevant phenomena for technological processes. One possible plasma-surface interaction is the generation of secondary electrons (SEs), which significantly influence the discharge when accelerated in t...
The electron dynamics and the mechanisms of power absorption in radio-frequency (RF) driven, magnetically enhanced capacitively coupled plasmas (MECCPs) at low pressure are investigated. The device in focus is a geometrically asymmetric cylindrical magnetron with a radially nonuniform magnetic field in axial direction and an electric field in radia...
The electron power absorption dynamics is investigated for radio-frequency (RF) argon capacitively coupled plasmas (CCPs) at low pressure (4-70 Pa) excited by a dual frequency waveform with frequencies of 27.12 MHz and 1.937 MHz. Based on the spatio-temporal dynamics of the ambipolar electric field a novel interpretation of the mechanism of frequen...
The rf voltage (blue) and the rf current density (red) at the driven electrode, (b) the electron and ion density profile, (c) and (d) the charge density, (e) and (f) the potential, and (g) and (h) the electric field. The left side presents spatiotemporal results, the solid black lines indicate the electron sheath edges, and the vertical black dashe...
Designing efficient plasma processes requires a fundamental understanding of the plasma properties and the underlying
physical chemistry. In this work, a pure oxygen plasma with its relatively simple reaction kinetics is chosen as a baseline
for such investigations, while at the same time acting as a pre-study for carbon dioxide. The globalKin code...
Bounded plasmas are characterized by a rapid but smooth transition from quasi-neutrality in the volume to electron depletion close to the electrodes and chamber walls. The thin non-neutral region, the boundary sheath, comprises only a small fraction of the discharge domain but controls much of its macroscopic behavior. Insights into the properties...
The physical characteristics of an argon discharge excited by a single-frequency harmonic waveform in the low-intermediate pressure regime (5-250 Pa) are investigated using Particle-in-Cell/Monte Carlo Collisions simulations. It is found that, when the pressure is increased, a non-negligible bulk electric field develops due to the presence of a ``p...
Radio-frequency-driven atmospheric pressure plasma jets (RF APPJs) play an essential role in many technological applications. This work studies the characteristics of these discharges in the so-called non-neutral regime where the conventional structure of a quasi-neutral bulk and an electron depleted sheath does not develop, and the electrons are i...
In atmospheric pressure capacitively-coupled microplasma jets, voltage waveform tailoring (VWT) was demonstrated to provide ultimate control of the electron energy distribution function (EEDF), which allows us to enhance and adjust the generation of selected neutral species by controlling the electron power absorption dynamics. However, at the fund...
Particle based simulations are indispensable tools for numerical studies of charged particle swarms and low-temperature plasma sources. The main advantage of such approaches is that they do not require any assumptions regarding the shape of the particle velocity/energy distribution function (VDF/EDF), but provide these basic quantities of kinetic t...
Bounded plasmas are characterized by a rapid but smooth transition from quasi-neutrality in the volume to electron depletion close to the electrodes and chamber walls. The thin non-neutral region, the boundary sheath, comprises only a small fraction of the discharge domain but controls much of its macroscopic behavior. Insights into the properties...
During the last years, atmospheric pressure plasmas have re-established themselves as a research focus. Radio-frequency driven atmospheric pressure plasma jets (here at the explicit example of the COST-Jet) are commonly used plasma sources for these studies. A characteristic feature of these atmospheric pressure plasma sources is the ratio between...
An argon–xenon (Ar/Xe) plasma is used as a model system for complex plasmas. Based on this system, symmetric low-pressure capacitively coupled radiofrequency discharges are examined utilizing particle-in-cell/Monte Carlo collisions simulations. In addition to the simulation, an analytical energy balance model fed with the simulation data is applied...
The electron momentum loss obtained from kinetic simulations, as well as the classical approximation based on the electron–neutral collision frequency, are calculated and compared in low pressure capacitively coupled plasmas in argon, helium and oxygen gases. The classical approximation (which is commonly used in theoretical or numerical fluid mode...
In atmospheric pressure capacitively coupled microplasma jets, Voltage Waveform Tailoring (VWT) was demonstrated to provide ultimate control of the Electron Energy Distribution Function (EEDF), which allows to enhance and adjust the generation of selected neutral species by controlling the electron power absorption dynamics. However, at the fundame...
Low pressure single- or dual-frequency capacitively coupled radio frequency (RF) plasmas are frequently used for high-aspect ratio (HAR) dielectric etching due to their capability to generate vertical ion bombardment of the wafer at high energies. Electrons typically reach the wafer at low energies and with a wide angular distribution during the lo...
For the self-consistent description of various plasma sources operated in the low-pressure (nonlocal, kinetic) regime, the Particle-In-Cell simulation approach, combined with the Monte Carlo treatment of collision processes (PIC/MCC), has become an important tool during the past decades. PIC/MCC simulation codes have been developed and maintained b...
An argon-xenon (Ar/Xe) plasma is used as a model system for complex plasmas. Based on this system, symmetric low-pressure capacitively coupled radio-frequency discharges are examined utilizing Particle-In-Cell/Monte Carlo Collisions (PIC/MCC) simulations. In addition to the simulation, an analytical energy balance model fed with the simulation data...
We present a spatio-temporally resolved analysis of electron power absorption in capacitively coupled argon plasmas at low pressures (1–10 Pa), based on the 1D momentum balance equation embedded into 1d3v particle-in-cell/Monte Carlo collisions simulations. In contrast to the predictions of theoretical models we find ‘Ohmic heating’ to be the domin...
In high aspect ratio (HAR) dielectric plasma etching, dual-frequency capacitively coupled radio-frequency plasmas operated at low pressures of 1 Pa or less are used. Such plasma sources are often driven by a voltage waveform that includes a low-frequency component in the range of hundreds of kHz with a voltage amplitude of 10 kV and more to generat...
In low temperature plasmas, the interaction of the electrons with the electric field is an important current research topic that is relevant for many applications. Particularly, in the low pressure regime (≤10 Pa), electrons can traverse a distance that may be comparable to the reactor dimensions without any collisions. This causes “nonlocal,” dyna...
A thorough understanding of the energy transfer mechanism from the electric field to electrons is of utmost importance for optimisation and control of different plasma sources and processes. This mechanism, called electron power absorption, involves complex electron dynamics in electronegative capacitively coupled plasmas (CCPs) at low pressures, t...
A thorough understanding of the energy transfer mechanism from the electric field to electrons is of utmost importance for optimization and control of different plasma sources and processes. This mechanism, called electron power absorption, involves complex electron dynamics in electronegative capacitively coupled plasmas (CCPs) at low pressures, t...
The etching of sub micrometer high-aspect-ratio (HAR) features into dielectric materials in low pressure radio frequency technological plasmas is limited by the accumulation of positive surface charges inside etch trenches. These are, at least partially, caused by highly energetic positive ions that are accelerated by the sheath electric field to h...
In simulation as well as analytical modeling studies of low-pressure capacitively coupled radio frequency (CCRF) discharges, the assumption of both a driving voltage source and a driving current source is commonly used. It is unclear, however, how and to what extent the choice of the mode of driving, that prescribes either a sinusoidal discharge vo...
Power absorption by electrons from the space- and time-dependent electric field represents the basic sustaining mechanism of all radio-frequency driven plasmas. This complex phenomenon has attracted significant attention. However, most theories and models are, so far, only able to account for part of the relevant mechanisms. The aim of this work is...
In particle-in-cell/Monte Carlo collisions (PIC/MCC) simulations of capacitively coupled plasmas (CCPs), the plasma-surface interaction is generally described by a simple model in which a constant secondary electron emission coefficient (SEEC) is assumed for ions bombarding the electrodes. In most PIC/MCC studies of CCPs, this coefficient is set to...
Measuring
plasma parameters, e.g. electron density and electron temperature, is an important procedure to verify the stability and behavior of a plasma
process. For this purpose the multipole resonance probe (MRP) represents a satisfying solution to measure the electron density. However the
influence of the probe on the plasma through its physical...
Low pressure capacitive radio frequency (RF) plasmas are often described by equivalent circuit models based on fluid approaches that predict the self-excitation of resonances, e.g., high frequency oscillations of the total current in asymmetric discharges, but do not provide a kinetic interpretation of these effects. In fact, they leave important q...
In low-pressure capacitive discharges the concept of Nonlinear Electron Resonance Heating (NERH) becomes important to enhance Ohmic dissipation. Particularly in geometrically asymmetric capacitive discharges (generation of a DC self-bias), the nonlinearities of the boundary plasma sheaths lead to a strongly non-sinusoidal radio frequency current. T...
In low-pressure capacitive discharges the radio-frequency modulated plasma sheaths generate a number of highly energetic beam electrons traversing the discharge gap. These electrons are important for sustaining the plasma via ionization. In this work, we investigate the dynamics of these electron beams as well as their effect on the plasma by means...
Die Messung von Plasmaparametern wie Elektronendichte und -temperatur während eines Plasmaprozesses ist eine wichtige Voraussetzung für eine Prozesssteuerung oder einer -überwachung.
Die aktive Plasma-Resonanzspektroskopie (APRS) stellt eine attraktive Diagnostikmethode für eine solche Überwachung dar, bei der die Eigenschaft von Plasmen, in der Nä...
In capacitively coupled radio frequency (CCRF) discharges at low pressures the electron heating is dominated by electron interaction with the plasma sheath. Especially the beams of the highly energetic electrons (of which the energy is much higher than the ionization threshold of the background gas), accelerated by the expanding plasma sheaths, pla...
The effect of changing the driving frequency on the plasma density and the
electron dynamics in a capacitive radio-frequency argon plasma operated at low
pressures of a few Pa is investigated by Particle in Cell/Monte Carlo
Collisions simulations and analytical modeling. In contrast to previous
assumptions the plasma density does not follow a quadr...
In low pressure (1 Pa) capacitively coupled radio-frequency discharges electron heating is dominated by stochastic heating. In this regime electron reflection from the modulated plasma sheaths can produce highly energetic electron beams, which traverse through the plasma bulk with small probability to undergo any collisions and interact with the op...
At very low gas pressures around 1 Pa the electron heating in capacitive radio frequency discharges is dominated by stochastic heating. In this regime electrons are accelerated by the oscillating sheaths, traverse through the plasma bulk and interact with the opposite sheath. Depending on the driving frequency the energetic electrons can enter the...
The electron heating in capacitive high frequency discharges at very low
gas pressures is dominated by momentum transfer from the oscillating
sheath. In this regime ohmic heating is not sufficient anymore to
maintain the plasma. Under certain electric and geometric conditions
highly energetic electrons are able to traverse the plasma bulk and
inter...