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  • 1.
    Alami, Jones
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics . Linköping University, The Institute of Technology.
    Gudmundsson, J. T.
    University of Iceland, Reykjavik.
    Böhlmark, Johan
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics . Linköping University, The Institute of Technology.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Helmersson, Ulf
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics . Linköping University, The Institute of Technology.
    Plasma dynamics in a highly ionized pulsed magnetron discharge2005In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 14, no 3, p. 525-531Article in journal (Refereed)
    Abstract [en]

    We report on electrostatic probe measurements of a high-power pulsed magnetron discharge. Space- and time-dependent characteristics of the plasma parameters are obtained as functions of the process parameters. By applying high-power pulses (peak power of ~0.5 MW), with a pulse-on time of ~100 µs and a repetition frequency of 20 ms, peak electron densities of the order of ~1019 m− 3, i.e. three orders of magnitude higher than for a conventional dc magnetron discharge, are achieved soon after the pulse is switched on. At high sputtering gas pressures (>5 mTorr), a second peak occurs in the electron density curve, hundreds of microseconds after the pulse is switched off. This second peak is mainly due to an ion acoustic wave in the plasma, reflecting off the chamber walls. This is concluded from the time delay between the two peaks in the electron and ion saturation currents, which is shown to be dependent on the chamber dimensions and the sputtering gas composition. Finally, the electron temperature is determined, initially very high but decreasing rapidly as the pulse is turned off. The reduction seen in the electron temperature, close to the etched area of the cathode, is due to cooling by the sputtered metal atoms.

  • 2.
    Berglund, Martin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Gruden, Mathias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Thornell, Greger
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Persson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Evaluation of a microplasma source based on a stripline split-ring resonator2013In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 22, no 5, p. 055017-Article in journal (Refereed)
    Abstract [en]

    In this paper, a stripline split-ring resonator microwave-induced plasma source, aimed for integration in complex systems, is presented and compared with a traditional microstrip design. Devices based on the two designs are evaluated using a plasma breakdown test setup for measuring the power required to ignite plasmas at different pressures. Moreover, the radiation efficiency of the devices is investigated with a Wheeler cap, and their electromagnetic compatibility is investigated in a variable electrical environment emulating an application. Finally, the basic properties of the plasma in the two designs are investigated in terms of electron temperature, plasma potential and ion density. The study shows that, with a minor increase in plasma ignition power, the stripline design provides a more isolated and easy-to-integrate alternative to the conventional microstrip design. Moreover, the stripline devices showed a decreased antenna efficiency as compared with their microstrip counterparts, which is beneficial for plasma sources. Furthermore, the investigated stripline devices exhibited virtually no frequency shift in a varying electromagnetic environment, whereas the resonance frequency of their microstrip counterparts shifted up to 17.5%. With regard to the plasma parameters, the different designs showed only minor differences in electron temperature, whereas the ion density was higher with the stripline design.

  • 3. Bohlmark, J.
    et al.
    Helmersson, U.
    VanZeeland, M.
    Axnäs, Ingvar
    KTH, Superseded Departments, Alfvén Laboratory.
    Alami, J.
    Brenning, Nils
    KTH, Superseded Departments, Alfvén Laboratory.
    Measurement of the magnetic field change in a pulsed high current magnetron discharge2004In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 13, no 4, p. 654-661Article in journal (Refereed)
    Abstract [en]

    In this paper we present a study of how the magnetic field of a circular planar magnetron is affected when it is exposed to a pulsed high current discharge. Spatially resolved magnetic field measurements are presented and the magnetic disturbance is quantified for different process parameters. The magnetic field is severely deformed by the discharge and we record changes of several millitesla, depending on the spatial location of the measurement. The shape of the deformation reveals the presence of azimuthally drifting electrons close to the target surface. Time resolved measurements show a transition between two types of magnetic perturbations. There is an early stage that is in phase with the axial discharge current and a late stage that is not in phase with the discharge current. The later part of the magnetic field deformation is seen as a travelling magnetic wave. We explain the magnetic perturbations by a combination of E x B drifting electrons and currents driven by plasma pressure gradients and the shape of the magnetic field. A plasma pressure wave is also recorded by a single tip Langmuir probe and the velocity (similar to10(3) m s(-1)) of the expanding plasma agrees well with the observed velocity of the magnetic wave. We note that the axial (discharge) current density is much too high compared to the azimuthal current density to be explained by classical collision terms, and an anomalous charge transport mechanism is required.

  • 4.
    Brenning, N
    et al.
    Royal Institute Technology.
    Huo, C
    Royal Institute Technology.
    Lundin, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Raadu, M A
    Royal Institute Technology.
    Vitelaru, C
    University of Paris 11.
    Stancu, G D
    University of Paris 11.
    Minea, T
    University of Paris 11.
    Helmersson, Ulf
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Understanding deposition rate loss in high power impulse magnetron sputtering: I. Ionization-driven electric fields2012In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 21, no 2, p. 025005-Article in journal (Refereed)
    Abstract [en]

    The lower deposition rate for high power impulse magnetron sputtering (HiPIMS) compared with direct current magnetron sputtering for the same average power is often reported as a drawback. The often invoked reason is back-attraction of ionized sputtered material to the target due to a substantial negative potential profile, sometimes called an extended presheath, from the location of ionization toward the cathode. Recent studies in HiPIMS devices, using floating-emitting and swept-Langmuir probes, show that such extended potential profiles do exist, and that the electric fields E-z directed toward the target can be strong enough to seriously reduce ion transport to the substrate. However, they also show that the potential drops involved can vary by up to an order of magnitude from case to case. There is a clear need to understand the underlying mechanisms and identify the key discharge variables that can be used for minimizing the back-attraction. We here present a combined theoretical and experimental analysis of the problem of electric fields E-z in the ionization region part of HiPIMS discharges, and their effect on the transport of ionized sputtered material. In particular, we have investigated the possibility of a sweet spot in parameter space in which the back-attraction of ionized sputtered material is low. It is concluded that a sweet spot might possibly exist for some carefully optimized discharges, but probably in a rather narrow window of parameters. As a measure of how far a discharge is from such a window, a Townsend product Pi(Townsend) is proposed. A parametric analysis of Pi(Townsend) shows that the search for a sweet spot is complicated by the fact that contradictory demands appear for several of the externally controllable parameters such as high/low working gas pressure, short/long pulse length, high/low pulse power and high/low magnetic field strength.

  • 5.
    Brenning, Nils
    et al.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Axnas, I.
    Raadu, Michael A.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Lundin, D.
    Helmerson, U.
    A bulk plasma model for dc and HiPIMS magnetrons2008In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 17, no 4Article in journal (Refereed)
    Abstract [en]

    A plasma discharge model has been developed for the bulk plasma (also called the extended presheath) in sputtering magnetrons. It can be used both for high power impulse magnetron sputtering (HiPIMS) and conventional dc sputtering magnetrons. Demonstration calculations are made for the parameters of the HiPIMS sputtering magnetron at Link "oping University, and also benchmarked against results in the literature on dc magnetrons. New insight is obtained regarding the structure and time development of the currents, the electric fields and the potential profiles. The transverse resistivity eta(perpendicular to) has been identified as having fundamental importance both for the potential profiles and for the motion of ionized target material through the bulk plasma. New findings are that in the HiPIMS mode, as a consequence of a high value of eta(perpendicular to), (1) there can be an electric field reversal that in our case extends 0.01-0.04m from the target, (2) the electric field in the bulk plasma is typically an order of magnitude weaker than in dc magnetrons, (3) in the region of electric field reversal the azimuthal current is diamagnetic in nature, i.e. mainly driven by the electron pressure gradient, and actually somewhat reduced by the electron Hall current which here has a reversed direction and (4) the azimuthal current above the racetrack can, through resistive friction, significantly influence the motion of the ionized fraction of the sputtered material and deflect it sideways, away from the target and towards the walls of the magnetron.

  • 6.
    Brenning, Nils
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering. KTH Royal Institute Technology, Sweden; University of Paris Saclay, France.
    Gudmundsson, J. T.
    KTH Royal Institute Technology, Sweden; University of Paris Saclay, France; University of Iceland, Iceland.
    Lundin, D.
    University of Paris Saclay, France.
    Minea, T.
    University of Paris Saclay, France.
    Raadu, M. A.
    KTH Royal Institute Technology, Sweden.
    Helmersson, Ulf
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering.
    The role of Ohmic heating in dc magnetron sputtering2016In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 25, no 6, article id 065024Article in journal (Refereed)
    Abstract [en]

    Sustaining a plasma in a magnetron discharge requires energization of the plasma electrons. In this work, Ohmic heating of electrons outside the cathode sheath is demonstrated to be typically of the same order as sheath energization, and a simple physical explanation is given. We propose a generalized Thornton equation that includes both sheath energization and Ohmic heating of electrons. The secondary electron emission yield gamma(SE) is identified as the key parameter determining the relative importance of the two processes. For a conventional 5 cm diameter planar dc magnetron, Ohmic heating is found to be more important than sheath energization for secondary electron emission yields below around 0.1.

  • 7.
    Brenning, Nils
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering. KTH Royal Institute Technology, Sweden; University of Paris Saclay, France.
    Gudmundsson, J. T.
    KTH Royal Institute Technology, Sweden; University of Paris Saclay, France; University of Iceland, Iceland.
    Raadu, M. A.
    KTH Royal Institute Technology, Sweden.
    Petty, T. J.
    University of Paris Saclay, France.
    Minea, T.
    University of Paris Saclay, France.
    Lundin, D.
    University of Paris Saclay, France.
    A unified treatment of self-sputtering, process gas recycling, and runaway for high power impulse sputtering magnetrons2017In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 26, no 12, article id 125003Article in journal (Refereed)
    Abstract [en]

    The combined processes of self-sputter (SS)-recycling and process gas recycling in high power impulse magnetron sputtering (HiPIMS) discharges are analyzed using the generalized recycling model (GRM). The study uses experimental data from discharges with current densities from the direct current magnetron sputtering range to the HiPIMS range, and using targets with self-sputter yields Y-SS from approximate to 0.1 to 2.6. The GRM analysis reveals that, above a critical current density of the order of J(crit) approximate to 0.2 A cm(-2), a combination of self-sputter recycling and gas-recycling is generally the case. The relative contributions of these recycling mechanisms, in turn, influence both the electron energy distribution and the stability of the discharges. For high self-sputter yields, above Y-SS approximate to 1, the discharges become dominated by SS-recycling, contain few hot secondary electrons from sheath energization, and have a relatively low electron temperature T-e. Here, stable plateau values of the discharge current develop during long pulses, and these values increase monotonically with the applied voltage. For low self-sputter yields, below Y-SS approximate to 0.2, the discharges above J(crit) are dominated by process gas recycling, have a significant sheath energization of secondary electrons and a higher T-e, and the current evolution is generally less stable. For intermediate values of YSS the discharge character gradually shifts between these two types. All of these discharges can, at sufficiently high discharge voltage, give currents that increase rapidly in time. For such cases we propose that a distinction should be made between unlimited runaway and limited runaway: in unlimited runaway the current can, in principle, increase without a limit for a fixed discharge voltage, while in limited runaway it can only grow towards finite, albeit very high, levels. For unlimited runway Y-SS amp;gt; 1 is found to be a necessary criterion, independent of the amount of gas-recycling in the discharge.

  • 8.
    Brenning, Nils
    et al.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics. Linköping University, Sweden; Université Paris-Sud, France.
    Gudmundsson, Jon Tomas
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Lundin, D.
    Minea, T.
    Raadu, Michael A.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics. Université Paris-Sud, France.
    Helmersson, U.
    The role of Ohmic heating in dc magnetron sputtering2016In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 25, no 6, article id 065024Article in journal (Refereed)
    Abstract [en]

    Sustaining a plasma in a magnetron discharge requires energization of the plasma electrons. In this work, Ohmic heating of electrons outside the cathode sheath is demonstrated to be typically of the same order as sheath energization, and a simple physical explanation is given. We propose a generalized Thornton equation that includes both sheath energization and Ohmic heating of electrons. The secondary electron emission yield gamma(SE) is identified as the key parameter determining the relative importance of the two processes. For a conventional 5 cm diameter planar dc magnetron, Ohmic heating is found to be more important than sheath energization for secondary electron emission yields below around 0.1.

  • 9.
    Brenning, Nils
    et al.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics. Laboratoire de Physique des Gaz et Plasmas—LPGP, UMR 8578 CNRS, Université Paris-Saclay, France; Plasma and Coatings Physics Division, IFM-Materials Physics, Linköping University, Sweden.
    Gudmundsson, Jon Tomas
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics. Laboratoire de Physique des Gaz et Plasmas—LPGP, UMR 8578 CNRS, Université Paris-Sud, Université Paris-Saclay, France; Science Institute, University of Iceland, Dunhaga 3, IS-107 Reykjavik, Iceland.
    Raadu, Michael A.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Petty, T. J.
    Universite Paris Sud.
    Minea, Tiberiu
    Unicersite Paris Sud.
    Lundin, Daniel
    Universite Paris Sud.
    A unified treatment of self-sputtering, process gas recycling, and runaway for high power impulse sputtering magnetrons2017In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 26, no 12, article id 125003Article in journal (Refereed)
    Abstract [en]

    The combined processes of self-sputter (SS)-recycling and process gas recycling in high power impulse magnetron sputtering (HiPIMS) discharges are analyzed using the generalized recycling model (GRM). The study uses experimental data from discharges with current densities from the direct current magnetron sputtering range to the HiPIMS range, and using targets with self-sputter yields Y-SS from approximate to 0.1 to 2.6. The GRM analysis reveals that, above a critical current density of the order of J(crit) approximate to 0.2 A cm(-2), a combination of self-sputter recycling and gas-recycling is generally the case. The relative contributions of these recycling mechanisms, in turn, influence both the electron energy distribution and the stability of the discharges. For high self-sputter yields, above Y-SS approximate to 1, the discharges become dominated by SS-recycling, contain few hot secondary electrons from sheath energization, and have a relatively low electron temperature T-e. Here, stable plateau values of the discharge current develop during long pulses, and these values increase monotonically with the applied voltage. For low self-sputter yields, below Y-SS approximate to 0.2, the discharges above J(crit) are dominated by process gas recycling, have a significant sheath energization of secondary electrons and a higher T-e, and the current evolution is generally less stable. For intermediate values of YSS the discharge character gradually shifts between these two types. All of these discharges can, at sufficiently high discharge voltage, give currents that increase rapidly in time. For such cases we propose that a distinction should be made between 'unlimited' runaway and 'limited' runaway: in unlimited runaway the current can, in principle, increase without a limit for a fixed discharge voltage, while in limited runaway it can only grow towards finite, albeit very high, levels. For unlimited runway Y-SS > 1 is found to be a necessary criterion, independent of the amount of gas-recycling in the discharge.

  • 10.
    Brenning, Nils
    et al.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Huo, Chunqing
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Lundin, Daniel
    Plasma and Coatings Physics Division, Linköping, Sweden.
    Raadu, Michael A.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Vitelaru, Catalin
    Stancu, Gabriel
    Minea, Tiberiu
    Helmersson, Ulf
    Understanding deposition rate loss in high power impulse magnetron sputtering: I. Ionization-driven electric fields2012In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 21, no 2, p. 025005-Article in journal (Refereed)
    Abstract [en]

    The lower deposition rate for high power impulse magnetron sputtering (HiPIMS) compared with direct current magnetron sputtering for the same average power is often reported as a drawback. The often invoked reason is back-attraction of ionized sputtered material to the target due to a substantial negative potential profile, sometimes called an extended presheath, from the location of ionization toward the cathode. Recent studies in HiPIMS devices, using floating-emitting and swept-Langmuir probes, show that such extended potential profiles do exist, and that the electric fields E-z directed toward the target can be strong enough to seriously reduce ion transport to the substrate. However, they also show that the potential drops involved can vary by up to an order of magnitude from case to case. There is a clear need to understand the underlying mechanisms and identify the key discharge variables that can be used for minimizing the back-attraction. We here present a combined theoretical and experimental analysis of the problem of electric fields E-z in the ionization region part of HiPIMS discharges, and their effect on the transport of ionized sputtered material. In particular, we have investigated the possibility of a 'sweet spot' in parameter space in which the back-attraction of ionized sputtered material is low. It is concluded that a sweet spot might possibly exist for some carefully optimized discharges, but probably in a rather narrow window of parameters. As a measure of how far a discharge is from such a window, a Townsend product Pi(Townsend) is proposed. A parametric analysis of Pi(Townsend) shows that the search for a sweet spot is complicated by the fact that contradictory demands appear for several of the externally controllable parameters such as high/low working gas pressure, short/long pulse length, high/low pulse power and high/low magnetic field strength.

  • 11.
    Butler, Alexandre
    et al.
    Univ Paris Saclay, France.
    Brenning, Nils
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering. Univ Paris Saclay, France; KTH Royal Inst Technol, Sweden.
    Raadu, Michael A.
    KTH Royal Inst Technol, Sweden.
    Gudmundsson, Jon Tomas
    KTH Royal Inst Technol, Sweden; Univ Iceland, Iceland.
    Minea, Tiberiu
    Univ Paris Saclay, France.
    Lundin, Daniel
    Univ Paris Saclay, France.
    On three different ways to quantify the degree of ionization in sputtering magnetrons2018In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 27, no 10, article id 105005Article in journal (Refereed)
    Abstract [en]

    Quantification and control of the fraction of ionization of the sputtered species are crucial in magnetron sputtering, and in particular in high-power impulse magnetron sputtering (HiPIMS), yet proper definitions of the various concepts of ionization are still lacking. In this contribution, we distinguish between three approaches to describe the degree (or fraction) of ionization: the ionized flux fraction F-flux, the ionized density fraction F-density, and the fraction a of the sputtered metal atoms that become ionized in the plasma (sometimes referred to as probability of ionization). By studying a reference HiPIMS discharge with a Ti target, we show how to extract absolute values of these three parameters and how they vary with peak discharge current. Using a simple model, we also identify the physical mechanisms that determine F-flux, F-density, and a as well as how these three concepts of ionization are related. This analysis finally explains why a high ionization probability does not necessarily lead to an equally high ionized flux fraction or ionized density fraction.

  • 12.
    Butler, Alexandre
    et al.
    Univ Paris Saclay, LPGP, UMR CNRS 8578, Univ Paris Sud, F-91405 Orsay, France..
    Brenning, Nils
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics. Univ Paris Saclay, LPGP, UMR CNRS 8578, Univ Paris Sud, F-91405 Orsay, France.; Linkoping Univ, Plasma & Coatings Phys Div, IFM Mat Phys, SE-58183 Linkoping, Sweden..
    Raadu, Michael A.
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Gudmundsson, Jon Tomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics. Univ Iceland, Sci Inst, Dunhaga 3, IS-107 Reykjavik, Iceland..
    Minea, Tiberiu
    Univ Paris Saclay, LPGP, UMR CNRS 8578, Univ Paris Sud, F-91405 Orsay, France..
    Lundin, Daniel
    Univ Paris Saclay, LPGP, UMR CNRS 8578, Univ Paris Sud, F-91405 Orsay, France..
    On three different ways to quantify the degree of ionization in sputtering magnetrons2018In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 27, no 10, article id 105005Article in journal (Refereed)
    Abstract [en]

    Quantification and control of the fraction of ionization of the sputtered species are crucial in magnetron sputtering, and in particular in high-power impulse magnetron sputtering (HiPIMS), yet proper definitions of the various concepts of ionization are still lacking. In this contribution, we distinguish between three approaches to describe the degree (or fraction) of ionization: the ionized flux fraction F-flux, the ionized density fraction F-density, and the fraction a of the sputtered metal atoms that become ionized in the plasma (sometimes referred to as probability of ionization). By studying a reference HiPIMS discharge with a Ti target, we show how to extract absolute values of these three parameters and how they vary with peak discharge current. Using a simple model, we also identify the physical mechanisms that determine F-flux, F-density, and a as well as how these three concepts of ionization are related. This analysis finally explains why a high ionization probability does not necessarily lead to an equally high ionized flux fraction or ionized density fraction.

  • 13.
    Giono, Gabriel
    et al.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics. Leibniz-Institute of Atmospheric Physics, Germany.
    Gudmundsson, Jon Tomas
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics. University of Iceland, Iceland.
    Ivchenko, Mykola
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Mazouffre, S.
    Dannenmayer, K.
    Loubere, D.
    Popelier, L.
    Merino, M.
    Olentsenko, Georgi
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Non-Maxwellian electron energy probability functions in the plume of a SPT-100 Hall thruster2018In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 27, no 1, article id 015006Article in journal (Refereed)
    Abstract [en]

    We present measurements of the electron density, the effective electron temperature, the plasma potential, and the electron energy probability function (EEPF) in the plume of a 1.5 kW-class SPT-100 Hall thruster, derived from cylindrical Langmuir probe measurements. The measurements were taken on the plume axis at distances between 550 and 1550 mm from the thruster exit plane, and at different angles from the plume axis at 550 mm for three operating points of the thruster, characterized by different discharge voltages and mass flow rates. The bulk of the electron population can be approximated as a Maxwellian distribution, but the measured distributions were seen to decline faster at higher energy. The measured EEPFs were best modelled with a general EEPF with an exponent a between 1.2 and 1.5, and their axial and angular characteristics were studied for the different operating points of the thruster. As a result, the exponent a from the fitted distribution was seen to be almost constant as a function of the axial distance along the plume, as well as across the angles. However, the exponent a was seen to be affected by the mass flow rate, suggesting a possible relationship with the collision rate, especially close to the thruster exit. The ratio of the specific heats, the. factor, between the measured plasma parameters was found to be lower than the adiabatic value of 5/3 for each of the thruster settings, indicating the existence of non-trivial kinetic heat fluxes in the near collisionless plume. These results are intended to be used as input and/or testing properties for plume expansion models in further work.

  • 14.
    Greiner, Franko
    et al.
    University of Kiel, Germany .
    Carstensen, Jan
    University of Kiel, Germany .
    Koehler, Nils
    University of Kiel, Germany .
    Pilch, Iris
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Ketelsen, Helge
    SENTECH Instruments GmbH, Germany .
    Knist, Sascha
    Graforce Hydro GmbH, Germany .
    Piel, Alexander
    University of Kiel, Germany .
    Imaging Mie ellipsometry: dynamics of nanodust clouds in an argon-acetylene plasma2012In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 21, no 6, p. 065005-Article in journal (Refereed)
    Abstract [en]

    For the in situ analysis of nano-sized particles in a laboratory plasma, Mie ellipsometry is a well established technique. We present a simple setup with two CCD cameras to gain online spatiotemporal resolved information of the growth dynamics of particles which are produced by plasma chemical processes in an argon-acetylene plasma. Imaging Mie ellipsometry proves to be a powerful technique to study the growth processes of nanodust in all its details.

  • 15.
    Gudmundsson, J. T.
    et al.
    KTH Royal Institute Technology, Sweden; University of Iceland, Iceland; University of Paris Saclay, France.
    Lundin, D.
    University of Paris Saclay, France.
    Brenning, Nils
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering. KTH Royal Institute Technology, Sweden.
    Raadu, M. A.
    KTH Royal Institute Technology, Sweden.
    Huo, Chunqing
    KTH Royal Institute Technology, Sweden.
    Minea, T. M.
    University of Paris Saclay, France.
    An ionization region model of the reactive Ar/O-2 high power impulse magnetron sputtering discharge2016In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 25, no 6, p. 065004-Article in journal (Refereed)
    Abstract [en]

    A new reactive ionization region model (R-IRM) is developed to describe the reactive Ar/O-2 high power impulse magnetron sputtering (HiPIMS) discharge with a titanium target. It is then applied to study the temporal behavior of the discharge plasma parameters such as electron density, the neutral and ion composition, the ionization fraction of the sputtered vapor, the oxygen dissociation fraction, and the composition of the discharge current. We study and compare the discharge properties when the discharge is operated in the two well established operating modes, the metal mode and the poisoned mode. Experimentally, it is found that in the metal mode the discharge current waveform displays a typical non-reactive evolution, while in the poisoned mode the discharge current waveform becomes distinctly triangular and the current increases significantly. Using the R-IRM we explore the current increase and find that when the discharge is operated in the metal mode Ar+ and Ti+ -ions contribute most significantly (roughly equal amounts) to the discharge current while in the poisoned mode the Ar+ -ions contribute most significantly to the discharge current and the contribution of O+ -ions, Ti+ -ions, and secondary electron emission is much smaller. Furthermore, we find that recycling of atoms coming from the target, that are subsequently ionized, is required for the current generation in both modes of operation. From the R-IRM results it is found that in the metal mode self-sputter recycling dominates and in the poisoned mode working gas recycling dominates. We also show that working gas recycling can lead to very high discharge currents but never to a runaway. It is concluded that the dominating type of recycling determines the discharge current waveform.

  • 16. Gudmundsson, Jon Tomas
    Experimental Studies of H2/Ar Plasma in a Planar Inductive Discharge1998In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 7, no 3, p. 330-336Article in journal (Refereed)
  • 17.
    Gudmundsson, Jon Tomas
    University of California; University of Iceland.
    Ion Energy Distribution in H2/Ar Plasma in a Planar Inductive Discharge1999In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 8, no 1, p. 58-64Article in journal (Refereed)
  • 18.
    Gudmundsson, Jon Tomas
    University of Iceland.
    On the effect of the electron energy distribution on the plasma parameters of argon discharge: A global (volume averaged) model study2001In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 19, no 1, p. 76-81Article in journal (Refereed)
  • 19.
    Gudmundsson, Jon Tomas
    et al.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics. University of Iceland, Iceland.
    Hannesdottir, Holmfridur
    University of Iceland.
    The role of the metastable O2(b) and energy-dependent secondary electron emission yields in capacitively coupled oxygen discharges2016In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 25, no 5, article id 055002Article in journal (Refereed)
    Abstract [en]

    The effects of including the singlet metastable molecule O2(b) in the discharge model of a capacitively coupled rf driven oxygen discharge are explored. We furthermore examine the addition of energy-dependent secondary electron emission yields from the electrodes to the discharge model. The one-dimensional object-oriented particle-in-cell Monte Carlo collision code oopd1 is used for this purpose, with the oxygen discharge model considering the species O2,(X3Σg -)O2(a1Σg),O2(b1Σg +), O(3P), O(1D), O2 +, O+, O-, and electrons. The effects on particle density profiles, the electron heating rate profile, the electron energy probability function and the sheath width are explored including and excluding the metastable oxygen molecules and secondary electron emission. Earlier we have demonstrated that adding the metastable O2(a1Σg) to the discharge model changes the electron heating from having contributions from both bulk and sheath heating to being dominated by sheath heating for pressures above 50 mTorr. We find that including the metastable O2(b1Σg +) further decreases the ohmic heating and the effective electron temperature in the bulk region. The effective electron temperature in the electronegative core is found to be less than 1 eV in the pressure range 50-200 mTorr which agrees with recent experimental findings. Furthermore, we find that including an energy-dependent secondary electron emission yield for -ions has a significant influence on the discharge properties, including decreased sheath width.

  • 20.
    Gudmundsson, Jon Tomas
    et al.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics. University of Iceland, Iceland.
    Hecimovic, Ante
    Institute for Experimental Physics II, Ruhr-University Bochum.
    Foundations of DC plasma sources2017In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 26, no 12, article id 123001Article in journal (Refereed)
  • 21.
    Gudmundsson, Jon Tomas
    et al.
    Shanghai Jiao Tong Universiy; University of Iceland; University of California.
    Kawamura, Emi
    University of California at Berkeley.
    Lieberman, Michael A.
    University of California at Berkeley.
    A benchmark study of a capacitively coupled oxygen discharge of the oopd1 particle-in-cell Monte Carlo code2013In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 22, no 3, article id 035011Article in journal (Refereed)
  • 22.
    Gudmundsson, Jon Tomas
    et al.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Lieberman, M. A.
    On the role of metastables in capacitively coupled oxygen discharges2015In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 24, no 3, article id 035016Article in journal (Refereed)
    Abstract [en]

    The roles of the metastable atoms O(D-1) and molecules O-2(a(1)Delta(g)) in a capacitively coupled rf driven oxygen discharge at 50 mTorr are explored using the one-dimensional object- oriented PIC/MCC code oopd1, which has one spatial dimension and three velocity components. The oxygen discharge model considers the species O2(X3 Sigma g-), O-2(a(1)Delta(g)) O(P-3), O(D-1), O-2(+), O+, O-, and electrons. The particle density profiles, the electron heating rate profile, the electron energy probability function and the ion energy distribution function at the grounded electrode are explored, including and/or excluding the metastables and secondary electron emission. We find that detachment by the metastable molecule O-2(a(1)Delta(g)) has a significant influence on the discharge properties such as the electronegativity, the effective electron temperature and the electron heating processes.

  • 23.
    Gudmundsson, Jon Tomas
    et al.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Lundin, D.
    Brenning, Nils
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Raadu, Michael A.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Huo, Chunqing
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Minea, T. M.
    An ionization region model of the reactive Ar/O-2 high power impulse magnetron sputtering discharge2016In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 25, no 6, article id 065004Article in journal (Refereed)
    Abstract [en]

    A new reactive ionization region model (R-IRM) is developed to describe the reactive Ar/O-2 high power impulse magnetron sputtering (HiPIMS) discharge with a titanium target. It is then applied to study the temporal behavior of the discharge plasma parameters such as electron density, the neutral and ion composition, the ionization fraction of the sputtered vapor, the oxygen dissociation fraction, and the composition of the discharge current. We study and compare the discharge properties when the discharge is operated in the two well established operating modes, the metal mode and the poisoned mode. Experimentally, it is found that in the metal mode the discharge current waveform displays a typical non-reactive evolution, while in the poisoned mode the discharge current waveform becomes distinctly triangular and the current increases significantly. Using the R-IRM we explore the current increase and find that when the discharge is operated in the metal mode Ar+ and Ti+ -ions contribute most significantly (roughly equal amounts) to the discharge current while in the poisoned mode the Ar+ -ions contribute most significantly to the discharge current and the contribution of O+ -ions, Ti+ -ions, and secondary electron emission is much smaller. Furthermore, we find that recycling of atoms coming from the target, that are subsequently ionized, is required for the current generation in both modes of operation. From the R-IRM results it is found that in the metal mode self-sputter recycling dominates and in the poisoned mode working gas recycling dominates. We also show that working gas recycling can lead to very high discharge currents but never to a runaway. It is concluded that the dominating type of recycling determines the discharge current waveform.

  • 24.
    Gudmundsson, Jon Tomas
    et al.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics. University of Iceland.
    Snorrason, D. I.
    Hannesdottir, H.
    The frequency dependence of the discharge properties in a capacitively coupled oxygen discharge2018In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 27, no 2, article id 025009Article in journal (Refereed)
    Abstract [en]

    We use the one-dimensional object-oriented particle-in-cell Monte Carlo collision code oopd1 to explore the evolution of the charged particle density profiles, electron heating mechanism, the electron energy probability function (EEPF), and the ion energy distribution in a single frequency capacitively coupled oxygen discharge, with driving frequency in the range 12-100 MHz. At a low driving frequency and low pressure (5 and 10 mTorr), a combination of stochastic (a-mode) and drift ambipolar (DA) heating in the bulk plasma (the electronegative core) is observed and the DA-mode dominates the time averaged electron heating. As the driving frequency or pressure are increased, the heating mode transitions into a pure a-mode, where electron heating in the sheath region dominates. At low pressure (5 and 10 mTorr), this transition coincides with a sharp decrease in electronegativity. At low pressure and low driving frequency, the EEPF is concave. As the driving frequency is increased, the number of low energy electrons increases and the relative number of higher energy electrons (> 10 eV) increases. At high driving frequency, the EEPF develops a convex shape or becomes bi-Maxwellian.

  • 25.
    Gudmundsson, Jon Tomas
    et al.
    University of Iceland.
    Thorsteinsson, E. G.
    Oxygen discharges diluted with argon: dissociation processes2007In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 16, no 2, p. 399-412Article in journal (Refereed)
    Abstract [en]

    We use a global (volume averaged) model to study the dissociationprocesses and the presence of negative ions and metastable species in a lowpressure high density O2/Ar discharge in the pressure range 1–100 mTorr.The electron density and the fractional dissociation of the oxygen moleculeincreases with increased argon content in the discharge. We relate thisincrease in fractional dissociation to an increase in the reaction rate forelectron impact dissociation of the oxygen molecule which is due to theincreased electron temperature with increased argon content in thedischarge. The electron temperature increases due to higher ionizationpotential of argon than for molecular and atomic oxygen. We find thecontribution of dissociation by quenching of the argon metastable Armbymolecular oxygen (Penning dissociation) to the creation of atomic oxygen tobe negligible. The negative oxygen ion O−is found to be the dominantnegative ion in the discharge. Dissociative attachment of the oxygenmolecule in the ground state O2(X3−g)and in particular the metastableoxygen molecule O2(a1g)are the dominating channels for creation of thenegative oxygen ion O−.(Some figures in this article are in colour only in the electronic version)

  • 26.
    Hasan, Mohammad I.
    et al.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics. Plasma and Coating Physics Division, IFM-Material Physics, Linköping University, SE-581 83, Linköping, Sweden .
    Pilch, I.
    Söderström, D.
    Lundin, Daniel
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Helmersson, U.
    Brenning, Nils
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Modeling the extraction of sputtered metal from high power impulse hollow cathode discharges2013In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 22, no 3, p. 035006-Article in journal (Refereed)
    Abstract [en]

    High power impulse hollow cathode sputtering is studied as a means to produce high fluxes of neutral and ionized sputtered metal species. A model is constructed for the understanding and optimization of such discharges. It relates input parameters such as the geometry of the cathode, the electric pulse form and frequency, and the feed gas flow rate and pressure, to the production, ionization, temperature and extraction of the sputtered species. Examples of processes that can be quantified by the use of the model are the internal production of sputtered metal and the degree of its ionization, the speed and efficiency of out-puffing from the hollow cathode associated with the pulses, and the gas back-flow into the hollow cathode between pulses. The use of the model is exemplified with a special case where the aim is the synthesis of nanoparticles in an expansion volume that lies outside the hollow cathode itself. The goals are here a maximum extraction efficiency, and a high degree of ionization of the sputtered metal. It is demonstrated that it is possible to reach a degree of ionization above 85%, and extraction efficiencies of 3% and 17% for the neutral and ionized sputtered components, respectively.

  • 27.
    Hasan, Mohammad
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology. Östergötlands Läns Landsting, Center for Diagnostics, Department of Clinical Pharmacology.
    Pilch, Iris
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology. Östergötlands Läns Landsting, Center for Diagnostics, Department of Clinical Pharmacology.
    Söderström, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology. Östergötlands Läns Landsting, Center for Diagnostics, Department of Clinical Pharmacology.
    Lundin, D.
    Royal Institute Technology KTH, Sweden.
    Helmersson, Ulf
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology. Östergötlands Läns Landsting, Center for Diagnostics, Department of Clinical Pharmacology.
    Brenning, N.
    Royal Institute Technology KTH, Sweden.
    Modeling the extraction of sputtered metal from high power impulse hollow cathode discharges2013In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 22, no 3, p. 035006-Article in journal (Refereed)
    Abstract [en]

    High power impulse hollow cathode sputtering is studied as a means to produce high fluxes of neutral and ionized sputtered metal species. A model is constructed for the understanding and optimization of such discharges. It relates input parameters such as the geometry of the cathode, the electric pulse form and frequency, and the feed gas flow rate and pressure, to the production, ionization, temperature and extraction of the sputtered species. Examples of processes that can be quantified by the use of the model are the internal production of sputtered metal and the degree of its ionization, the speed and efficiency of out-puffing from the hollow cathode associated with the pulses, and the gas back-flow into the hollow cathode between pulses. The use of the model is exemplified with a special case where the aim is the synthesis of nanoparticles in an expansion volume that lies outside the hollow cathode itself. The goals are here a maximum extraction efficiency, and a high degree of ionization of the sputtered metal. It is demonstrated that it is possible to reach a degree of ionization above 85%, and extraction efficiencies of 3% and 17% for the neutral and ionized sputtered components, respectively.

  • 28. Hollenstein, C.
    et al.
    Dorier, J. -L
    Dutta, J.
    Sansonnens, L.
    Howling, A. A.
    Diagnostics of particle genesis and growth in RF silane plasmas by ion mass spectrometry and light scattering1994In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 3, no 3, p. 278-285Article in journal (Refereed)
  • 29. Huang, Shuo
    et al.
    Gudmundsson, Jon Tomas
    Shanghai Jiao Tong University; University of Iceland.
    A current driven capacitively coupled chlorine discharge2014In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 23, no 2, article id 025015Article in journal (Refereed)
  • 30. Huang, Shuo
    et al.
    Gudmundsson, Jon Tomas
    Shanghai Jiao Tong University; University of Iceland.
    Dual frequency capacitively coupled chlorine discharge2015In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 24, no 1, article id 015003Article in journal (Refereed)
    Abstract [en]

    The effect of the control parameters of both high and low frequency sources on a dual-frequency capacitively coupled chlorine discharge is systematically investigated using a hybrid approach, which consists of a particle-in-cell/Monte Carlo simulation and a volume-averaged global model. The high frequency current density is varied from 20 to 80Am-2, the driving high frequency is varied from 27.12 to 100MHz, and the driving low frequency is varied from 1 to 13.56MHz, while the low frequency current density is kept at 1Am-2. The discharge pressure is maintained at 10mTorr. Key plasma parameters (including the electron heating rate, the electron energy probability function, the ion flux, the ion energy, and angular distributions) are explored and their variations with the control parameters are analyzed and compared with other discharge chemistries. As the high frequency current increases, the electron heating is enhanced in the sheath region and is diminished in the bulk region, showing a transition of the electron heating from the drift-ambipolar mode to the α mode. The fluxes of ions and high-energy Cl2 molecules reaching the surface decrease with an increase in the driving high frequency, and the average sheath potential is approximately inversely proportional to the driving high frequency. The electron heating rate, the fluxes of and Cl+ ions reaching the surface, and the average sheath potential show little dependence on the driving low frequency, while the profile of the ion energy distribution evolves from a broad bimodal profile to a narrow single-peak profile as the driving low frequency increases, which corresponds to the transition of the discharge from the intermediate frequency regime to the high frequency regime.

  • 31.
    Huo, Chunqing
    et al.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Lundin, Daniel
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics. Plasma and Coatings Physics Division.
    Raadu, Michael A.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Anders, André
    Gudmundsson, Jon Tomas
    KTH, School of Electrical Engineering (EES).
    Brenning, Nils
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    On sheath energization and Ohmic heating in sputtering magnetrons2013In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 22, no 4, p. 045005-Article in journal (Refereed)
    Abstract [en]

    In most models of sputtering magnetrons, the mechanism for energizing the electrons in the discharge is assumed to be sheath energization. In this process, secondary emitted electrons from the cathode surface are accelerated across the cathode sheath into the plasma, where they either ionize directly or transfer energy to the local lower energy electron population that subsequently ionizes the gas. In this work, we present new modeling results in support of an alternative electron energization mechanism. A model is experimentally constrained, by a fitting procedure, to match a set of experimental data taken over a large range in discharge powers in a high-power impulse magnetron sputtering (HiPIMS) device. When the model is matched to real data in this way, one finding is that the discharge can run with high power and large gas rarefaction without involving the mechanism of secondary electron emission by twice-ionized sputtered metal. The reason for this is that direct Ohmic heating of the plasma electrons is found to dominate over sheath energization by typically an order of magnitude. This holds from low power densities, as typical for dc magnetrons, to so high powers that the discharge is close to self-sputtering, i.e. dominated by the ionized vapor of the sputtered gas. The location of Ohmic heating is identified as an extended presheath with a potential drop of typically 100-150V. Such a feature, here indirectly derived from modeling, is in agreement with probe measurements of the potential profiles in other HiPIMS experiments, as well as in conventional dc magnetrons.

  • 32.
    Huo, Chunqing
    et al.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Lundin, Daniel
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics. Plasma and Coatings Physics Division.
    Raadu, Michael A.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Anders, André
    Gudmundsson, Jon Tomas
    KTH, School of Electrical Engineering (EES). University of Iceland.
    Brenning, Nils
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    On the road to self-sputtering in high power impulse magnetron sputtering: particle balance and discharge characteristics2014In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 23, no 2, p. 025017-Article in journal (Refereed)
    Abstract [en]

    The onset and development of self-sputtering (SS) in a high power impulse magnetron sputtering (HiPIMS) discharge have been studied using a plasma chemical model and a set of experimental data, taken with an aluminum target and argon gas. The model is tailored to duplicate the discharge in which the data are taken. The pulses are long enough to include both an initial transient and a following steady state. The model is used to unravel how the internal discharge physics evolves with pulse power and time, and how it is related to features in the discharge current-voltage-time characteristics such as current densities, maxima, kinks and slopes. The connection between the self-sputter process and the discharge characteristics is quantified and discussed in terms of three parameters: a critical target current density J(crit) based on the maximum refill rate of process (argon) gas above the target, an SS recycling factor Pi(SS-recycle), and an approximation alpha a of the probabilities of ionization of species that come from the target (both sputtered metal and embedded argon atoms). For low power pulses, discharge voltages UD <= 380V with peak current densities below approximate to 0.2A cm(-2), the discharge is found to be dominated by process gas sputtering. In these pulses there is an initial current peak in time, associated with partial gas rarefaction, which is followed by a steady-state-like plateau in all parameters similar to direct current magnetron sputtering. In contrast, high power pulses, with U-D >= 500V and peak current densities above J(D) approximate to 1.6Acm(-2), make a transition to a discharge mode where SS dominates. The transition is found not to be driven by process gas rarefaction which is only about 10% at this time. Maximum gas rarefaction is found later in time and always after the initial peak in the discharge current. With increasing voltage, and pulse power, the discharge can be described as following a route where the role of SS increases in four steps: process gas sputtering, gas-sustained SS, self-sustained SS and SS runaway. At the highest voltage, 1000V, the discharge is very close to, but does not go into, the SS runaway mode. This absence of runaway is proposed to be connected to an unexpected finding: that twice ionized ions of the target species play almost no role in this discharge, not even at the highest powers. This reduces ionization by secondary-emitted energetic electrons almost to zero in the highest power range of the discharge.

  • 33.
    Huo, Chunqing
    et al.
    Royal Institute Technology, Sweden .
    Raadu, Michael A
    Royal Institute Technology, Sweden .
    Lundin, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Gudmundsson, Jon Tomas
    Shanghai Jiao Tong University, Peoples R China University of Iceland, Iceland .
    Anders, Andre
    University of Calif Berkeley, CA 94720 USA .
    Brenning, Nils
    Royal Institute Technology, Sweden .
    Gas rarefaction and the time evolution of long high-power impulse magnetron sputtering pulses2012In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 21, no 4, p. 045004-Article in journal (Refereed)
    Abstract [en]

    Model studies of 400 mu s long discharge pulses in high-power impulse magnetron sputtering have been made to study the gas dynamics and plasma chemistry in this type of pulsed processing plasma. Data are taken from an experiment using square voltage pulses applied to an Al target in an Ar atmosphere at 1.8 Pa. The study is limited to low power densities, andlt; 0.5 kW cm(-2), in which the discharge is far away from the runaway self-sputtering mode. The model used is the ionization region model, a time-dependent plasma chemistry discharge model developed for the ionization region in magnetron sputtering discharges. It gives a close fit to the discharge current during the whole pulse, both an initial high-current transient and a later plateau value of constant lower current. The discharge current peak is found to precede a maximum in gas rarefaction of the order of Delta n(Ar)/n(Ar),(0) approximate to 50%. The time durations of the high-current transient, and of the rarefaction maximum, are determined by the time it takes to establish a steady-state diffusional refill of process gas from the surrounding volume. The dominating mechanism for gas rarefaction is ionization losses, with only about 30% due to the sputter wind kick-out process. During the high-current transient, the degree of sputtered metal ionization reaches 65-75%, and then drops to 30-35% in the plateau phase. The degree of self-sputtering (defined here as the metal ion fraction of the total ion current to the target) also varies during the pulse. It grows from zero at pulse start to a maximum of 65-70% coinciding in time with the maximum gas rarefaction, and then stabilizes in the range 40-45% during the plateau phase. The loss in deposition rate that can be attributed to the back-attraction of the ionized sputtered species is also estimated from the model. It is low during the initial 10-20 mu s, peaks around 60% during the high-current transient, and finally stabilizes around 30% during the plateau phase.

  • 34.
    Huo, Chunqing
    et al.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Raadu, Michael A.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Lundin, Daniel
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Gudmundsson, Jon Tomas
    Anders, André
    Brenning, Nils
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Gas rarefaction and the time evolution of long high-power impulse magnetron sputtering pulses2012In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 21, no 4, p. 045004-Article in journal (Refereed)
    Abstract [en]

    Model studies of 400 mu s long discharge pulses in high-power impulse magnetron sputtering have been made to study the gas dynamics and plasma chemistry in this type of pulsed processing plasma. Data are taken from an experiment using square voltage pulses applied to an Al target in an Ar atmosphere at 1.8 Pa. The study is limited to low power densities, < 0.5 kW cm(-2), in which the discharge is far away from the runaway self-sputtering mode. The model used is the ionization region model, a time-dependent plasma chemistry discharge model developed for the ionization region in magnetron sputtering discharges. It gives a close fit to the discharge current during the whole pulse, both an initial high-current transient and a later plateau value of constant lower current. The discharge current peak is found to precede a maximum in gas rarefaction of the order of Delta n(Ar)/n(Ar),(0) approximate to 50%. The time durations of the high-current transient, and of the rarefaction maximum, are determined by the time it takes to establish a steady-state diffusional refill of process gas from the surrounding volume. The dominating mechanism for gas rarefaction is ionization losses, with only about 30% due to the sputter wind kick-out process. During the high-current transient, the degree of sputtered metal ionization reaches 65-75%, and then drops to 30-35% in the plateau phase. The degree of self-sputtering (defined here as the metal ion fraction of the total ion current to the target) also varies during the pulse. It grows from zero at pulse start to a maximum of 65-70% coinciding in time with the maximum gas rarefaction, and then stabilizes in the range 40-45% during the plateau phase. The loss in deposition rate that can be attributed to the back-attraction of the ionized sputtered species is also estimated from the model. It is low during the initial 10-20 mu s, peaks around 60% during the high-current transient, and finally stabilizes around 30% during the plateau phase.

  • 35. Lundin, Daniel
    et al.
    Al Sahab, Seham
    Brenning, Nils
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Huo, Chunqing
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Helmersson, Ulf
    Internal current measurements in high power impulse magnetron sputtering2011In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 20, no 4, p. 045003-Article in journal (Refereed)
    Abstract [en]

    The transport of charged particles in a high power impulse magnetron sputtering (HiPIMS) discharge is of considerable interest when optimizing this promising deposition technique with respect to deposition rate and control of the ion acceleration. In this study the internal current densities J(phi) (azimuthal direction) and J(z) (axial direction) have therefore been spatially and temporally resolved in the bulk plasma region above a cylindrical magnetron using Rogowski coils. From the measurements a phenomenological model has been constructed describing the evolution of the current density in this pulsed plasma. The core of the model is based on three different types of current systems, which characterize the operating transport mechanisms, such as current transport along and across magnetic field lines. There is a gradual change between these current systems during the initiation, build-up and steady state of a HiPIMS plasma. Furthermore, the data also show that there are spatial and temporal variations of the key transport parameter J(phi)/J(z), governing the cross-B resistivity and also the energy of the charged particles. The previously reported faster-than-Bohm cross-B electron transport is verified here, but not for all locations. These results on the plasma dynamics are essential input when modeling the axial electric field, governing the back-attraction of ionized sputtered material, and might furthermore provide a link between the different resistivities reported in HiPIMS, pulsed-DC, and DC magnetron discharges.

  • 36.
    Lundin, Daniel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Al Sahab, Seham
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Brenning, Nils
    Division of Space and Plasma Physics, School of Electrical Engineering, Royal Institute of Technology, SE-100 44 Stockholm, Sweden.
    Huo, Chunqing
    Division of Space and Plasma Physics, School of Electrical Engineering, Royal Institute of Technology, SE-100 44 Stockholm, Sweden.
    Helmersson, Ulf
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Internal current measurements in high power impulse magnetron sputtering2011In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 20, no 4, p. 045003-Article in journal (Refereed)
    Abstract [en]

    The transport of charged particles in a high power impulse magnetron sputtering (HiPIMS) discharge is of great interest when optimizing this promising deposition technique with respect to deposition rate and control of the ion acceleration. In this study the internal current densities Jϕ (azimuthal direction) and JD⊥ (axial direction) have therefore been spatially and temporally resolved in the bulk plasma region above a cylindrical magnetron using Rogowski coils. From the measurements a phenomenological model has been constructed describing the evolution of the current density in this pulsed plasma. The core of the model is based on six different types of current systems, which characterize the operating transport mechanisms, such as current transport along and across magnetic field lines, as well as the initiation, buildup and steady-state of a HiPIMS plasma. Furthermore, the data also shows that there are spatial and temporal variations of the key transport parameter Jϕ/JD⊥ , governing the cross-B resistivity and also the energy of the charged particles. The previously reported faster-than-Bohm cross-B electron transport is here verified, but is not found to be present during the whole discharge regime as well as for all locations. These results on the plasma dynamics are essential input when modeling the axial electric field, governing the back-attraction of ionized sputtered material, and might furthermore provide a link between the different resistivities reported in HiPIMS, pulsed-DC, and DC magnetron discharges.

  • 37. Lundin, Daniel
    et al.
    Brenning, Nils
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Jadernas, Daniel
    Larsson, Petter
    Wallin, Erik
    Lattemann, Martina
    Raadu, Michael A.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Helmersson, Ulf
    Transition between the discharge regimes of high power impulse magnetron sputtering and conventional direct current magnetron sputtering2009In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 18, no 4Article in journal (Refereed)
    Abstract [en]

    Current and voltage have been measured in a pulsed high power impulse magnetron sputtering (HiPIMS) system for discharge pulses longer than 100 mu s. Two different current regimes could clearly be distinguished during the pulses: (1) a high-current transient followed by (2) a plateau at lower currents. These results provide a link between the HiPIMS and the direct current magnetron sputtering (DCMS) discharge regimes. At high applied negative voltages the high-current transient had the characteristics of HiPIMS pulses, while at lower voltages the plateau values agreed with currents in DCMS using the same applied voltage. The current behavior was found to be strongly correlated with the chamber gas pressure, where increasing gas pressure resulted in increasing peak current and plateau current. Based on these experiments it is suggested here that the high-current transients cause a depletion of the working gas in the area in front of the target, and thereby a transition to a DCMS-like high-voltage, lower current regime.

  • 38. Lundin, Daniel
    et al.
    Helmersson, Ulf
    Kirkpatrick, Scott
    Rohde, Suzanne
    Brenning, Nils
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Anomalous electron transport in high power impulse magnetron sputtering2008In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 17, no 2Article in journal (Refereed)
    Abstract [en]

    Oscillating electric fields in the megahertz range have been studied in a high power impulse magnetron sputtering (HIPIMS) plasma with the use of electric field probe arrays. One possible reason for these oscillations to occur is charge perturbation-or so-called modified two-stream instabilities (MTSIs). It is known that MTSIs give rise to acceleration of the charged plasma species and can give a net transport of electrons across the magnetic field lines. Measurements of these oscillations confirm trends, specifically of the frequency dependence on ion mass and magnetic field strength as expected from the theory of MTSI waves. These results help to explain the previously reported anomalous fast electron transport in HIPIMS discharges, where classical theory of diffusion using collisions to transport electrons has failed.

  • 39. Lundin, Daniel
    et al.
    Larsson, Petter
    Wallin, Erik
    Lattemann, Martina
    Brenning, Nils
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Helmersson, Ulf
    Cross-field ion transport during high power impulse magnetron sputtering2008In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 17, no 3Article in journal (Refereed)
    Abstract [en]

    In this study, the effect on thin film growth due to an anomalous electron transport, found in high power impulse magnetron sputtering (HiPIMS), has been investigated for the case of a planar circular magnetron. An important consequence of this type of transport is that it affects the way ions are being transported in the plasma. It was found that a significant fraction of ions are transported radially outwards in the vicinity of the cathode, across the magnetic field lines, leading to increased deposition rates directly at the side of the cathode ( perpendicular to the target surface). Furthermore, this mass transport parallel to the target surface leads to that the fraction of sputtered material reaching a substrate placed directly in front of the target is substantially lower in HiPIMS compared with conventional direct current magnetron sputtering (dcMS). This would help to explain the lower deposition rates generally observed for HiPIMS compared with dcMS. Moreover, time-averaged mass spectrometry measurements of the energy distribution of the cross-field transported ions were carried out. The measured distributions show a direction-dependent high-energy tail, in agreement with predictions of the anomalous transport mechanism.

  • 40.
    Lundin, Daniel
    et al.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Čada, Martin
    Hubička, Zdeněk
    Ionization of sputtered Ti, Al, and C coupled with plasma characterization in HiPIMS2015In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 24, no 3, article id 035018Article in journal (Refereed)
    Abstract [en]

    The ionization of sputtered Ti, Al, and C has been investigated in non-reactive high-power impulse magnetron sputtering discharges using Ar as a process gas. Two complementary techniques, time-resolved Langmuir probe diagnostics and a recently developed gridless ion meter, have for the first time been used to estimate absolute values of the ionized fractions of the sputtered material. To cover a range of commonly used discharge conditions we have carried out measurements for different process gas pressures, discharge current densities, and pulse lengths. It is found that by increasing the current density from 0.5 to 2.0 A cm(-2) there is a general increase of n(e) independently of target material and position in time with maximum plasma densities of about 1 x 10(18)-5 x 10(18) m(-3) above the target race track. Also the ionized flux fraction, measured by ion meter, is increased when increasing the current density and reaches a maximum value of 78% in the Al discharge. By using the recorded n(e) and T-e values to calculate the ionization probability of the sputtered material, and benchmark these results using the ion meter, we also show that Langmuir probe diagnostics is a useful tool to estimate trends and changes in the degree of ionization for different process conditions.

  • 41. Niyonzima, S.
    et al.
    Pop, N.
    Iacob, F.
    Larson, Åsa
    Stockholm University, Faculty of Science, Department of Physics.
    Orel, A. E.
    Mezei, J. Zs
    Chakrabarti, K.
    Laporta, V.
    Hassouni, K.
    Benredjem, D.
    Bultel, A.
    Tennyson, J.
    Reiter, D.
    Schneider, I. F.
    Low-energy collisions between electrons and BeD+2018In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 27, no 2, article id 025015Article in journal (Refereed)
    Abstract [en]

    Multichannel quantum defect theory is applied in the treatment of the dissociative recombination and vibrational excitation processes for the BeD+ ion in the 24 vibrational levels of its ground electronic state (X (1)Sigma(+), v(i)(+) = 0 ... 23). Three electronic symmetries of BeD** states ((2)Pi, (2)Sigma(+), and (2)Delta) are considered in the calculation of cross sections and the corresponding rate coefficients. The incident electron energy range is 10(-5)-2.7 eV and the electron temperature range is 100-5000 K. The vibrational dependence of these collisional processes is highlighted. The resulting data are useful in magnetic confinement fusion edge plasma modeling and spectroscopy, in devices with beryllium based main chamber materials, such as ITER and JET, and operating with the deuterium-tritium fuel mix. An extensive rate coefficients database is presented in graphical form and also by analytic fit functions whose parameters are tabulated in the supplementary material.

  • 42.
    Proto, A.
    et al.
    Univ Iceland, Sci Inst, Dunhaga 3, IS-107 Reykjavik, Iceland..
    Gudmundsson, Jon Tomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics. Univ Iceland, Sci Inst, Dunhaga 3, IS-107 Reykjavik, Iceland.
    The role of surface quenching of the singlet delta molecule in a capacitively coupled oxygen discharge2018In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 27, no 7, article id 074002Article in journal (Refereed)
    Abstract [en]

    We use the one-dimensional object-oriented particle-in-cell Monte Carlo collision code oopd1 to explore the influence of the surface quenching of the singlet delta metastable molecule O-2(a(1)Delta(g)) on the electron heating mechanism, and the electron energy probability function (EEPF), in a single frequency capacitively coupled oxygen discharge. When operating at low pressure (10 mTorr) varying the surface quenching coefficient in the range 0.000 01-0.1 has no influence on the electron heating mechanism and electron heating is dominated by drift-ambipolar (DA) heating in the plasma bulk and electron cooling is observed in the sheath regions. As the pressure is increased to 25 mTorr the electron heating becomes a combination of DA-mode and alpha-mode heating, and the role of the DA-mode decreases with decreasing surface quenching coefficient. At 50 mTorr, electron heating in the sheath region dominates. However, for the highest quenching coefficient there is some contribution from the DA-mode in the plasma bulk, but this contribution decreases to almost zero and pure alpha-mode electron heating is observed for a surface quenching coefficient of 0.001 or smaller.

  • 43.
    Raadu, Michael
    et al.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Axnäs, Ingvar
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Gudmundsson, Jon Tomas
    Shanghai Jiao Tong University; University of Iceland.
    Huo, Chunqing
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Brenning, Nils
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    An ionization region model for high-power impulse magnetron sputtering discharges2011In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 20, no 6, p. 065007-Article in journal (Refereed)
    Abstract [en]

    A time-dependent plasma discharge model has been developed for the ionization region in a high-power impulse magnetron sputtering (HiPIMS) discharge. It provides a flexible modeling tool to explore, e. g., the temporal variations of the ionized fractions of the working gas and the sputtered vapor, the electron density and temperature, and the gas rarefaction and refill processes. A separation is made between aspects that can be followed with a certain precision, based on known data, such as excitation rates, sputtering and secondary emission yield, and aspects that need to be treated as uncertain and defined by assumptions. The input parameters in the model can be changed to fit different specific applications. Examples of such changes are the gas and target material, the electric pulse forms of current and voltage, and the device geometry. A basic version, ionization region model I, using a thermal electron population, singly charged ions, and ion losses by isotropic diffusion is described here. It is fitted to the experimental data from a HiPIMS discharge in argon operated with 100 mu s long pulses and a 15 cm diameter aluminum target. Already this basic version gives a close fit to the experimentally observed current waveform, and values of electron density n(e), the electron temperature T(e), the degree of gas rarefaction, and the degree of ionization of the sputtered metal that are consistent with experimental data. We take some selected examples to illustrate how the model can be used to throw light on the internal workings of these discharges: the effect of varying power efficiency, the gas rarefaction and refill during a HiPIMS pulse, and the mechanisms determining the electron temperature.

  • 44. Stancu, G. D.
    et al.
    Brenning, Nils
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics. Université Paris-Sud, France.
    Vitelaru, C.
    Lundin, D.
    Minea, T.
    Argon metastables in HiPIMS: Validation of the ionization region model by direct comparison to time resolved tunable diode-laser diagnostics2015In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 24, no 4, article id 045011Article in journal (Refereed)
    Abstract [en]

    The volume plasma interactions of high power impulse magnetron sputtering (HiPIMS) discharges operated with a Ti target is analyzed in detail by combining time-resolved diagnostics with modeling of plasma kinetics. The model employed is the ionization region model (IRM) with an improved and detailed treatment of the kinetics of the argon metastable (Arm) state, called m-IRM. The diagnostics used is tunable diode-laser absorption spectroscopy (TD-LAS) of the Arm state, which gives the line-of-sight density integrated along the laser path parallel to the target surface. The TD-LAS recordings exhibit quite complex temporal evolutions Arm(t), with distinct features that are shown to reflect the time evolution of the plasma (the electron density and temperature), and of the argon gas (gas rarefaction and refill). The Arm(t) function is thus a tracer for the most important aspects of internal discharge physics, and therefore suitable for model testing and validation. The IRM model is constructed to be locked to obey specific experimental macroscopic discharge parameters, specifically the discharge current I<inf>D</inf>(t) and the voltage U<inf>D</inf>(t). It has to this purpose been run with the appropriate process gas pressures (from 0.67 to 2.67 Pa), with the experimentally applied voltage pulse profiles U<inf>D</inf>(t), and with the resulting current pulse profiles I<inf>D</inf>(t) (with maxima from 0.5 to 70 A). It is shown that the model reproduces the features in the TD-LAS measurements: both the Arm(t) evolution in single pulses, and how the pulse shapes change with gas pressure and with pulse amplitude. The good agreement between the measurements and model output is in this work taken to validate the basic assumptions of the m-IRM. In addition, the m-IRM results have been used to unravel the connections between volume plasma kinetics and various features recorded in the TD-LAS measurement, and to generalize the foremost characteristics of the studied discharges.

  • 45. Thorsteinsson, E. G.
    et al.
    Gudmundsson, Jon Tomas
    University of Iceland.
    A global (volume averaged) model of a chlorine discharge2010In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 19, no 1, article id 015001Article in journal (Refereed)
  • 46. Thorsteinsson, E. G.
    et al.
    Gudmundsson, Jon Tomas
    University of Iceland.
    A global (volume averaged) model of the nitrogen discharge: I. Steady State2009In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 18, no 4, article id 045001Article in journal (Refereed)
  • 47. Thorsteinsson, E. G.
    et al.
    Gudmundsson, Jon Tomas
    University of Iceland.
    A global (volume averaged) model of the nitrogen discharge: II. Pulsed Power Modulation2009In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 18, no 4, article id 045002Article in journal (Refereed)
  • 48.
    Toneli, D. A.
    et al.
    Univ Fed Sao Paulo, Dept Sci & Technol, BR-12231280 Sao Jose Dos Campos, Brazil..
    Pessoa, R. S.
    Technol Inst Aeronaut, Dept Phys, BR-12228900 Sao Jose Dos Campos, Brazil..
    Roberto, M.
    Technol Inst Aeronaut, Dept Phys, BR-12228900 Sao Jose Dos Campos, Brazil..
    Gudmundsson, Jon Tomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics. Univ Iceland, Sci Inst, Dunhaga 3, IS-107 Reykjavik, Iceland.
    A global model study of low pressure high density CF4 discharge2019In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 28, no 2, article id 025007Article in journal (Refereed)
    Abstract [en]

    We present a revised reaction set for low pressure high density CF4 plasma modelling. A global model (volume averaged) was developed to study a CF4 discharge that includes the neutral species CF4, CF3, CF2, CF, F-2, F, and C, the metastable states CF(a(4)Sigma(-) ) and CF2(B-3(1)), the positive ions CF3+, CF2+, CF+, CF2+, F+ and C+, the negative ions CF3-, F-2(-), and F- and electrons. The main reactions that contribute to the production and loss of each species are pointed out with an emphasis on the radicals CF2, CF and F, the dominant positive ion CF3+, and the dominant negative ion F-. We find wall processes to have a significant influence on the discharge. The density of F-2 is high due to recombination of F atoms at the walls and the losses of the radicals F, CF, and CF3 are mainly through wall recombination. As the pressure is increased, F- becomes the dominant negative charged species. The discharge is found to be weakly electronegative below similar to 10 mTorr and the electronegativity decreases with increased absorbed power.

  • 49. Vitelaru, C.
    et al.
    Lundin, D.
    Stancu, G. D.
    Brenning, Nils
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Bretagne, J.
    Minea, T.
    Argon metastables in HiPIMS: time-resolved tunable diode-laser diagnostics2012In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 21, no 2, p. 025010-Article in journal (Refereed)
    Abstract [en]

    Time-resolved tunable diode-laser absorption spectroscopy measurements were performed on the argon metastable (Ar-m) level 3s(2)3p(5)(P-2(3/2)degrees)4s excited at 801.478 nm, in the dense plasma region in front of the magnetron target in a high power impulse magnetron sputtering (HiPIMS) discharge. From the Doppler profile the evolution of the temperature and density was derived during the pulse as well as during the plasma decay, i.e. in the afterglow. It is shown that the Ar-m density sharply increases at the beginning of the discharge pulse, followed by a severe Ar-m depletion along with increasing gas temperature around the peak of the HiPIMS discharge current. The strong dynamics of these parameters involve many elementary processes such as electron-impact excitation, electron-impact de-excitation and ionization of Ar-m, gas rarefaction, electron temperature increase at the end of the pulse and gas diffusion. These phenomena are discussed with respect to several parameters: distance from the target, peak discharge current during the pulse, pulse length, and gas pressure.

  • 50.
    Vitelaru, C
    et al.
    University of Paris 11.
    Lundin, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Stancu, G D
    University of Paris 11.
    Brenning, N
    Royal Institute of Technology.
    Bretagne, J
    University of Paris 11.
    Minea, T
    University of Paris 11.
    Argon metastables in HiPIMS: time-resolved tunable diode-laser diagnostics2012In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 21, no 2, p. 025010-Article in journal (Refereed)
    Abstract [en]

    Time-resolved tunable diode-laser absorption spectroscopy measurements were performed on the argon metastable (Ar-m) level 3s(2)3p(5)(P-2(3/2)degrees)4s excited at 801.478 nm, in the dense plasma region in front of the magnetron target in a high power impulse magnetron sputtering (HiPIMS) discharge. From the Doppler profile the evolution of the temperature and density was derived during the pulse as well as during the plasma decay, i.e. in the afterglow. It is shown that the Ar-m density sharply increases at the beginning of the discharge pulse, followed by a severe Ar-m depletion along with increasing gas temperature around the peak of the HiPIMS discharge current. The strong dynamics of these parameters involve many elementary processes such as electron-impact excitation, electron-impact de-excitation and ionization of Ar-m, gas rarefaction, electron temperature increase at the end of the pulse and gas diffusion. These phenomena are discussed with respect to several parameters: distance from the target, peak discharge current during the pulse, pulse length, and gas pressure.

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