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  • 1. Agnarsson, Björn
    et al.
    Magnus, Fridrik
    Tryggvason, T. K.
    Ingason, Arni S.
    Leosson, K
    Olafsson, S
    Gudmundsson, Jon Tomas
    University of Iceland.
    Rutile TiO2 thin films grown by reactive high power impulse magnetron sputtering2013In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 545, p. 445-450Article in journal (Refereed)
  • 2. Agustsson, J. S.
    et al.
    Agustsson, B. V.
    Eriksson, A. K.
    Gylfason, Kristinn B.
    KTH, School of Electrical Engineering (EES), Microsystem Technology (Changed name 20121201).
    Olafsson, S.
    Johnsen, K.
    Gudmundsson, J. T.
    Hydrogen uptake in MgO thin films grown by reactive magnetron sputtering2006Conference paper (Other academic)
    Abstract
  • 3. Agustsson, J. S.
    et al.
    Arnalds, U. B.
    Ingason, A. S.
    Gylfason, Kristinn B.
    KTH, School of Electrical Engineering (EES), Microsystem Technology (Changed name 20121201).
    Johnsen, K.
    Olafsson, S.
    Gudmundsson, Jon Tomas
    University of Iceland, Iceland.
    Electrical resistivity and morphology of ultra thin Pt films grown by dc magnetron sputtering on SiO(2)2008In: Journal of Physics Conference Series, IOP Science , 2008, Vol. 100Conference paper (Refereed)
    Abstract [en]

    Ultra thin platinum films were grown by dc magnetron sputtering on thermally oxidized Si (100) substrates. The electrical resistance of the films was monitored in-situ during growth. The coalescence thickness was determined for various growth temperatures and found to increase from 1.3 nm for films grown at room temperature to 1.8 nm for films grown at 250 degrees C, while a continuous film was formed at a thickness of 3.9 nm at room temperature and 3.5 nm at 250 degrees C. The electrical resistivity increases with increased growth temperature, as well as the morphological grain size, and the surface roughness, measured with a scanning tunneling microscope (STM).

  • 4. Agustsson, J. S.
    et al.
    Arnalds, U. B.
    Ingason, A. S.
    Gylfason, Kristinn B.
    KTH, School of Electrical Engineering (EES), Microsystem Technology (Changed name 20121201).
    Johnsen, K.
    Olafsson, S.
    Gudmundsson, Jon Tomas
    University of Iceland, Iceland.
    Growth, coalescence, and electrical resistivity of thin Pt films grown by dc magnetron sputtering on SiO22008In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 254, no 22, p. 7356-7360Article in journal (Refereed)
    Abstract [en]

    Ultra thin platinum films were grown by dc magnetron sputtering on thermally oxidized Si (100) substrates. The electrical resistance of the films was monitored in situ during growth. The coalescence thickness was determined for various growth temperatures and found to increase from 1.1 nm for films grown at room temperature to 3.3 nm for films grown at 400 degrees C. A continuous film was formed at a thickness of 2.9 nm at room temperature and 7.5 nm at 400 degrees C. The room temperature electrical resistivity decreases with increased growth temperature, while the in-plain grain size and the surface roughness, measured with a scanning tunneling microscope (STM), increase. Furthermore, the temperature dependence of the film electrical resistance was explored at various stages during growth.

  • 5. Agustsson, Jon S.
    et al.
    Gylfason, Kristinn B.
    KTH, School of Electrical Engineering (EES), Microsystem Technology (Changed name 20121201).
    Olafsson, Sveinn
    Johnsen, Kristinn
    Gudmundsson, Jon T
    Electrical properties of thin MgO films2005Conference paper (Other academic)
  • 6. Arnalds, U. B.
    et al.
    Agustsson, J. S.
    Ingason, A. S.
    Eriksson, A. K.
    Gylfason, Kristinn B.
    KTH, School of Electrical Engineering (EES), Microsystem Technology (Changed name 20121201).
    Gudmundsson, J. T.
    Olafsson, S.
    A magnetron sputtering system for the preparation of patterned thin films and in situ thin film electrical resistance measurements2007In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 78, no 10, p. 103901-Article in journal (Refereed)
    Abstract [en]

    We describe a versatile three gun magnetron sputtering system with a custom made sample holder for in situ electrical resistance measurements, both during film growth and ambient changes on film electrical properties. The sample holder allows for the preparation of patterned thin film structures, using up to five different shadow masks without breaking vacuum. We show how the system is used to monitor the electrical resistance of thin metallic films during growth and to study the thermodynamics of hydrogen uptake in metallic thin films. Furthermore, we demonstrate the growth of thin film capacitors, where patterned films are created using shadow masks.

  • 7. Bohlmark, J.
    et al.
    Lattemann, M.
    Gudmundsson, J. T.
    Ehiasarian, A. P.
    Gonzalvo, Y. Aranda
    Brenning, Nils
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Helmersson, U.
    The ion energy distributions and ion flux composition from a high power impulse magnetron sputtering discharge2006In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 515, no 4, p. 1522-1526Article in journal (Refereed)
    Abstract [en]

    The energy distribution of sputtered and ionized metal atoms as well as ions from the sputtering gas is reported for a high power impulse magnetron sputtering (HIPIMS) discharge. High power pulses were applied to a conventional planar circular magnetron Ti target. The peak power on the target surface was 1-2 kW/cm(2) with a duty factor of about 0.5%. Time resolved, and time averaged ion energy distributions were recorded with an energy resolving quadrupole mass spectrometer. The ion energy distributions recorded for the HIPIMS discharge are broader with maximum detected energy of 100 eV and contain a larger fraction of highly energetic ions (about 50% with E-i > 20 eV) as compared to a conventional direct current magnetron sputtering discharge. The composition of the ion flux was also determined, and reveals a high metal fraction. During the most intense moment of the discharge, the ionic flux consisted of approximately 50% Ti1+, 24% Ti2+, 23% Ar1+, and 3% Ar2+ ions.

  • 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.
    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.

  • 11.
    Gudmundsson, J. T.
    et al.
    KTH, Superseded Departments, Solid Mechanics.
    Alami, J.
    Gylfason, Kristinn B.
    KTH, School of Electrical Engineering (EES), Microsystem Technology (Changed name 20121201).
    Bohlmark, J.
    Helmersson, U.
    Plasma Dynamics in an Unipolar Pulsed Magnetron Sputtering Discharge2004Conference paper (Refereed)
  • 12. Gudmundsson, J. T.
    et al.
    Brenning, Nils
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Lundin, D.
    Helmersson, U.
    High power impulse magnetron sputtering discharge2012In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 30, no 3, p. 030801-Article, review/survey (Refereed)
    Abstract [en]

    The high power impulse magnetron sputtering (HiPIMS) discharge is a recent addition to plasma based sputtering technology. In HiPIMS, high power is applied to the magnetron target in unipolar pulses at low duty cycle and low repetition frequency while keeping the average power about 2 orders of magnitude lower than the peak power. This results in a high plasma density, and high ionization fraction of the sputtered vapor, which allows better control of the film growth by controlling the energy and direction of the deposition species. This is a significant advantage over conventional dc magnetron sputtering where the sputtered vapor consists mainly of neutral species. The HiPIMS discharge is now an established ionized physical vapor deposition technique, which is easily scalable and has been successfully introduced into various industrial applications. The authors give an overview of the development of the HiPIMS discharge, and the underlying mechanisms that dictate the discharge properties. First, an introduction to the magnetron sputtering discharge and its various configurations and modifications is given. Then the development and properties of the high power pulsed power supply are discussed, followed by an overview of the measured plasma parameters in the HiPIMS discharge, the electron energy and density, the ion energy, ion flux and plasma composition, and a discussion on the deposition rate. Finally, some of the models that have been developed to gain understanding of the discharge processes are reviewed, including the phenomenological material pathway model, and the ionization region model.

  • 13. 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)
  • 14.
    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)
  • 15.
    Gudmundsson, Jon Tomas
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics. University of Iceland, Iceland.
    On reactive high power impulse magnetron sputtering2015In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 58, no 1Article in journal (Refereed)
    Abstract [en]

    High power impulse magnetron sputtering (HiPIMS) is an ionized physical vapor deposition (IPVD) technique that is particularly promising for reactive sputtering applications. However, there are few issues that have to be resolved before the full potential of this technique can be realized. Here we give an overview of the key experimental findings for the reactive HiPIMS discharge. An increase in the discharge current is commonly observed with increased partial pressure of the reactive gas or decreased repetition pulse frequency. There are somewhat conflicting claims regarding the hysteresis effect in the reactive HiPIMS discharge as some report reduction or elimination of the hysteresis effect while others claim a feedback control is essential. The ion energy distribution of the metal ion and the atomic ion of the reactive gas are similar and extend to very high energies while the ion energy distribution of the working gas and the molecular ion of the reactive gas are similar and are much less energetic.

  • 16.
    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)
  • 17.
    Gudmundsson, Jon Tomas
    University of Iceland.
    The high power impulse magnetron sputtering discharge as an ionized physical vapor deposition tool2010In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 84, no 12, p. 1360-1364Article in journal (Refereed)
    Abstract [en]

    Various magnetron sputtering tools have been developed that provide a high degree of ionization of the sputtered vapor referred to as ionized physical vapor deposition (IPVD). The ions can be controlled with respect to energy and direction as they arrive to the growth surface which allows for increased control of film properties during growth. Here, the design parameters for IPVD systems are briefly reviewed. The first sputter based IPVD systems utilized a secondary plasma source between the target and the substrate in order to generate a highly ionized sputtered vapor. High power impulse magnetron sputtering (HiPIMS) is a recent sputtering technique that utilizes IPVD where a high density plasma is created by applying high power pulses at low frequency and low duty cycle to a magnetron sputtering device. A summary of the key experimental findings for the HiPIMS discharge is given. Measurements of the temporal and spatial behavior of the plasma parameters indicate electron density peak, that expands from the target with a fixed velocity. The discharge develops from an inert sputtering gas dominated to a sputtered vapor dominated during the pulse. The high electron density results in a high degree of ionization of the deposition material.

  • 18. Gudmundsson, Jon Tomas
    The Ion Energy Distribution in a Planar Inductive Oxygen Discharge1999In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 32, no 7, p. 798-803Article in journal (Refereed)
  • 19.
    Gudmundsson, Jon Tomas
    et al.
    University of Iceland.
    Alami, J
    Linköping University.
    Helmersson, Ulf
    Linköping University.
    Evolution of the electron energy distribution and the plasma parameters in a pulsed magnetron discharge2001In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 78, no 22, p. 3427-3429Article in journal (Refereed)
  • 20.
    Gudmundsson, Jon Tomas
    et al.
    University of Iceland.
    Alami, J
    Linköping University.
    Helmersson, Ulf
    Linköping University.
    Spatial and Temporal Behavior of the Plasma Parameters in a Pulsed Magnetron Discharge2002In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 161, no 2-3, p. 249-256Article in journal (Refereed)
  • 21.
    Gudmundsson, Jon Tomas
    et al.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics. University of Iceland, Iceland.
    Hannesdottir, H.
    The role of the singlet metastables in capacitively coupled oxygen discharges2016In: 2016 IEEE International Conference on Plasma Science (ICOPS), Institute of Electrical and Electronics Engineers (IEEE), 2016Conference paper (Refereed)
    Abstract [en]

     Summary form only given. We use the one-dimensional object-oriented particle-in-cell Monte Carlo collision code oopd1 to study the evolution of the charged particle density profiles, electron heating mechanism, effective electron temperature, and the electron energy probability function (EEPF) in a capacitively coupled oxygen discharge with pressure in the pressure range of 10-500 mTorr. We find that at higher pressure (50-500 mTorr) the electron heating occurs mainly in the sheath region, and detachment by the metastable singlet molecule O2(b1Δg) has a significant influence on the electron heating process and the EEPF [1,2]. At a low pressure (10 mTorr), Ohmic heating in the bulk plasma (the electronegative core) dominates, and detachment by O2(b1Δg) has only a small influence on the heating process. Thus at low pressure, the EEPF is convex and as the pressure is increased the number of low energy electrons increases and the number of higher energy electrons (>10 eV) decreases, and the EEPF develops a concave shape or becomes bi-Maxwellian [2]. Furthermore, we explore the effects of including the singlet metastable molecule O2(b1Σg) and energy-dependent secondary electron emission yields at the electrodes in a capacitively coupled single frequency rf driven oxygen discharge. We find that including the metastable O2(b1Δg) further decreases the Ohmic heating in the bulk region at higher pressures. Moreover, we find that including an energy-dependent secondary electron emission yield for O2+-ions has a significant influence on the discharge properties while the energy dependent secondary electron emission coefficient due to O+-ions and the neutrals has only marginal influence on the discharge properties.

  • 22.
    Gudmundsson, Jon Tomas
    et al.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics. University of Iceland, Iceland.
    Hannesdottir, Holmfridur
    On the role of metastable states in low pressure oxygen discharges2017In: AIP Conference Proceedings, American Institute of Physics (AIP), 2017, Vol. 1811, article id 120001Conference paper (Refereed)
    Abstract [en]

    We use the one-dimensional object-oriented particle-in-cell Monte Carlo collision code oopd1 to explore the spatio-temporal evolution of the electron heating mechanism in a capacitively coupled oxygen discharge in the pressure range 10 – 200 mTorr. The electron heating is most significant in the sheath vicinity during the sheath expansion phase. We explore how including and excluding detachment by the singlet metastable states O2(a1 Δg) and O2(b1Σ+g) influences the heating mechanism, the effective electron temperature and electronegativity, in the oxygen discharge. We demonstrate that the detachment processes have a significant influence on the discharge properties, in particular for the higher pressures. At 10 mTorr the time averaged electron heating shows mainly ohmic heating in the plasma bulk (the electronegative core) and at higher pressures there is no ohmic heating in the plasma bulk, that is electron heating in the sheath regions dominates.

  • 23.
    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.

  • 24.
    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)
  • 25.
    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)
  • 26.
    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.

  • 27.
    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.

  • 28.
    Gudmundsson, Jon Tomas
    et al.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Lundin, D.
    Raadu, Michael A.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Minea, T.
    Brenning, Nils
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    The current waveform in reactive high power impulse magnetron sputtering2016In: 2016 IEEE International Conference on Plasma Science (ICOPS), Institute of Electrical and Electronics Engineers (IEEE), 2016Conference paper (Refereed)
    Abstract [en]

    Summary form only given. The understanding of the current waveform for the non-reactive HiPIMS discharge is now rather well established [1,2]. It is described by a rise in the current to an initial peak and then a drop followed by a stable plateau. The drop is a result of a strong gas compression due to the sudden large flux of atoms from the target. For the reactive HiPIMS discharge striking differences are observed and those seem to depend on the mode of operation, the reactive gas and the target material. The discharge current waveform changes in shape as well as in the peak value when the target surface enters the poisoned mode. For Ar/O2 discharge with Ti target the discharge current waveform varies with oxygen partial pressure and pulse repetition frequency [3]. For the higher repetition frequencies the familiar nonreactive current waveform is observed. As the repetition frequency is lowered there is an increase in the current which transits into a different waveform as the repetition frequency is decreased further. The waveform observed at low repetition frequency is similar to the one observed at high reactive gas flow rate. Similarly, the current waveform in the reactive Ar/N2 HiPIMS discharge with Ti target is highly dependent on the pulse repetition frequency and the current is found to increase significantly as the frequency is lowered [4]. However, the discharge current keeps its shape and it remains as for the non-reactive case as the current increases. These findings will be compared with results for various combinations of gas mixtures and targets found in the literature [5]. Furthermore, we explore the current waveform in reactive HiPIMS using the ionization region model (IRM) [6] of the reactive Ar/O2 discharge with a Ti target. We discuss the current waveform development and how the discharge composition varies between metal and poisoned mode.

  • 29.
    Gudmundsson, Jon Tomas
    et al.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics. University of Iceland, Iceland.
    Lundin, D.
    Stancu, G. D.
    Brenning, Nils
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics. Linköping University, Sweden.
    Minea, T. M.
    Are the argon metastables important in high power impulse magnetron sputtering discharges?2015In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 22, no 11, article id 113508Article in journal (Refereed)
    Abstract [en]

    We use an ionization region model to explore the ionization processes in the high power impulse magnetron sputtering (HiPIMS) discharge in argon with a titanium target. In conventional dc magnetron sputtering (dcMS), stepwise ionization can be an important route for ionization of the argon gas. However, in the HiPIMS discharge stepwise ionization is found to be negligible during the breakdown phase of the HiPIMS pulse and becomes significant (but never dominating) only later in the pulse. For the sputtered species, Penning ionization can be a significant ionization mechanism in the dcMS discharges, while in the HiPIMS discharge Penning ionization is always negligible as compared to electron impact ionization. The main reasons for these differences are a higher plasma density in the HiPIMS discharge, and a higher electron temperature. Furthermore, we explore the ionization fraction and the ionized flux fraction of the sputtered vapor and compare with recent experimental work.

  • 30.
    Gudmundsson, Jon Tomas
    et al.
    University of Iceland.
    Marakhtanov, A M
    Patel, K. K.
    Gopinath, V. P.
    Lieberman, M. A.
    On the Plasma Parameters of a Planar Inductive Oxygen Discharge2000In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 33, p. 1323-1331Article in journal (Refereed)
  • 31.
    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.

  • 32.
    Gudmundsson, Jon Tomas
    et al.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics. University of Iceland, Iceland.
    Snorrason, David I.
    University of Iceland.
    On electron heating in a low pressure capacitively coupled oxygen discharge2017In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 122, no 19, article id 193302Article in journal (Refereed)
  • 33.
    Gudmundsson, Jon Tomas
    et al.
    University of Iceland.
    Svavarsson, H G
    Gislason, H P
    Lithium-gold-related complexes in p-type crystalline silicon1999In: Physica B, Vol. 273-274, p. 379-382Article in journal (Refereed)
  • 34.
    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)

  • 35.
    Gudmundsson, Jon Tomas
    et al.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics. University of Iceland, Iceland.
    Ventejou, Bruno
    The pressure dependence of the discharge properties in a capacitively coupled oxygen discharge2015In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 118, no 15, article id 153302Article 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, and the electron energy probability function (EEPF) in a capacitively coupled oxygen discharge with pressure in the pressure range of 10-500 mTorr. We find that at higher pressure (50-500 mTorr) the electron heating occurs mainly in the sheath region, and detachment by the metastable singlet molecule O-2(a(1)Delta(g)) has a significant influence on the electron heating process. At a low pressure (10 mTorr), Ohmic heating in the bulk plasma (the electronegative core) dominates, and detachment by O-2(a(1)Delta(g)) has only a small influence on the heating process. Thus at low pressure, the EEPF is convex and as the pressure is increased the number of low energy electrons increases and the number of higher energy electrons (> 10 eV) decreases, and the EEPF develops a concave shape or becomes bi-Maxwellian.

  • 36.
    Gylfason, Kristinn B.
    et al.
    KTH, School of Electrical Engineering (EES), Microsystem Technology (Changed name 20121201).
    Agustsson, J. S.
    Olafsson, S.
    Meyvantsson, I.
    Johnsen, K.
    Gudmundsson, J. T.
    Ultra-thin Lattice Matched Cr_xMo_1-x/MgO Multilayers2004Conference paper (Refereed)
    Abstract
  • 37.
    Gylfason, Kristinn B.
    et al.
    Lyfjathroun Biopharmaceuticals, Iceland.
    Ingason, A. S.
    Agustsson, J. S.
    Olafsson, S.
    Johnsen, K.
    Gudmundsson, J. T.
    In-situ resistivity measurements during growth of ultra-thin Cr_0.7Mo_0.32006In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 515, no 2, p. 583-586Article in journal (Refereed)
    Abstract [en]

    The growth of ultra-thin, lattice matched, Cr0.7Mo0.3 films on an MgO substrate, in a dc magnetron discharge, was investigated by in situ measurements in order to determine the minimum thickness of a continuous layer. The thickness dependence of the resistivity shows a coalescence thickness of less than two monolayers indicating layer by layer growth of the films. We compare the resistivity of the films to a combination of the Fuchs- Sondheimer and the Mayadas-Shatzkes models, assuming a thickness dependence of grain size. The model indicates that grain size increases with increasing growth temperature.

  • 38.
    Hajihoseini, Hamidreza
    et al.
    University of Iceland.
    Gudmundsson, Jon Tomas
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics. University of Iceland.
    Vanadium and vanadium nitride thin films grown by high power impulse magnetron sputtering2017In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 50, no 50, article id 505302Article in journal (Refereed)
    Abstract [en]

    Thin vanadium and vanadium nitride films were grown on SiO2 by non-reactive and reactive high power impulse magnetron sputtering (HiPIMS), respectively. The film properties were compared to films grown by conventional dc magnetron sputtering (dcMS) at similar conditions. We explored the influence of the stationary magnetic confinement field strength on the film properties and the process parameters. The deposition rate is much lower for non-reactive sputtering by HiPIMS than for dcMS. Furthermore, for both dcMS and HiPIMS the deposition rate is lower for strong magnetic confinement. Structural characterization was carried out using x-ray diffraction and reflection methods as well as atomic force microscopy and scanning electron microscope. Both dcMS and HiPIMS grown vanadium films are polycrystalline with similar grain size regardless of magnetic field strength. For dcMS grown vanadium films the surface roughness is higher when a strong magnetic field is used. For both non-reactive growth of vanadium and reactive growth of vanadium nitride the HiPIMS process produces denser films with lower surface roughness than dcMS does. Lowering the magnetic field strength increases the deposition rate significantly for reactive HiPIMS while it increases only slightly in the reactive dcMS case. The films grown by HiPIMS with strong magnetic confinement exhibit higher density and lower roughness. We find that the operating pressure, growth temperature, discharge voltage and film thickness has influence on the properties of HiPIMS grown vanadium nitride films. The films are denser when grown at high temperature, high discharge voltage and low pressure. The density of those films is lower for thicker films and thicker films consist of larger grain size. For all the films explored, higher density coincides with lower surface roughness. Thus, the deposition method, magnetic field strength, growth temperature, discharge voltage, film thickness and growth pressure have a significant influence on the film quality and structural properties, including the grain size for the various orientations.

  • 39.
    Hannesdottir, Holmfridur
    et al.
    University of Iceland.
    Gudmundsson, Jon Tomas
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics. University of Iceland, Iceland.
    On singlet metastable states, ion flux and ion energy in single and double frequency capacitively coupled oxygen discharges2017In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 50, no 17, article id 175201Article in journal (Refereed)
    Abstract [en]

    We apply particle-in-cell simulations with Monte Carlo collisions to study the influence of the singlet metastable states on the ion energy distribution in single and dual frequency capacitively coupled oxygen discharges. For this purpose, the one-dimensional object-oriented particle-in-cell Monte Carlo collision code oopd1 is used, in which the discharge model includes the following nine species: electrons, the neutrals O(3P) and O), the negative ions O, the positive ions O+ and O, and the metastables O(1D), O and O2(b). Earlier, we have explored the effects of adding the species O) and O2(b), and an energy-dependent secondary electron emission yield for oxygen ions and neutrals, to the discharge model. We found that including the two molecular singlet metastable states decreases the ohmic heating and the effective electron temperature in the bulk region (the electronegative core). Here we explore how these metastable states influence dual frequency discharges consisting of a fundamental frequency and the lowest even harmonics. Including or excluding the detachment reactions of the metastables O) and O2(b) can shift the peak electron temperature from the grounded to the powered electrode or vice versa, depending on the phase difference of the two applied frequencies. These metastable states can furthermore significantly influence the peak of the ion energy distribution for O-ions bombarding the powered electrode, and hence the average ion energy upon bombardment of the electrode, and lower the ion flux.

  • 40. Hannesdottir, Holmfridur
    et al.
    Gudmundsson, Jon Tomas
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics. University of Iceland, Reykjavik, Iceland.
    On singlet metastable states, ion flux and ion energy in single and dual frequency capacitively coupled oxygen discharges2017In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 50, no 17, article id 175201Article in journal (Refereed)
    Abstract [en]

    We apply particle-in-cell simulations with Monte Carlo collisions to study the influence of the singlet metastable states on the ion energy distribution in single and dual frequency capacitively coupled oxygen discharges. For this purpose, the one-dimensional object-oriented particle-in-cell Monte Carlo collision code oopd1 is used, in which the discharge model includes the following nine species: electrons, the neutrals O(3P) and O), the negative ions O, the positive ions O+ and O, and the metastables O(1D), O and O2(b). Earlier, we have explored the effects of adding the species O) and O2(b), and an energy-dependent secondary electron emission yield for oxygen ions and neutrals, to the discharge model. We found that including the two molecular singlet metastable states decreases the ohmic heating and the effective electron temperature in the bulk region (the electronegative core). Here we explore how these metastable states influence dual frequency discharges consisting of a fundamental frequency and the lowest even harmonics. Including or excluding the detachment reactions of the metastables O) and O2(b) can shift the peak electron temperature from the grounded to the powered electrode or vice versa, depending on the phase difference of the two applied frequencies. These metastable states can furthermore significantly influence the peak of the ion energy distribution for O-ions bombarding the powered electrode, and hence the average ion energy upon bombardment of the electrode, and lower the ion flux.

  • 41. Hecimovic, Ante
    et al.
    Gudmundsson, Jon Tomas
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics. University of Iceland.
    Preface to Special Topic: Reactive high power impulse magnetron sputtering2017In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 121, no 17, article id 171801Article in journal (Refereed)
  • 42. Helmersson, Ulf
    et al.
    Latteman, M
    Bohlmark, J
    Ehiasarian, A. P.
    Gudmundsson, Jon Tomas
    University of Iceland.
    Ionized Physical Vapor Deposition (IPVD): A Review of Technology and Applications2006In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 513, p. 1-24Article in journal (Refereed)
    Abstract [en]

    In plasma-based deposition processing, the importance of low-energy ion bombardment during thin film growth can hardly be exaggerated. Ion bombardment is an important physical tool available to materials scientists in the design of new materials and new structures. Glow discharges and in particular, the magnetron sputtering discharge have the advantage that the ions of the discharge are abundantly available to the deposition process. However, the ion chemistry is usually dominated by the ions of the inert sputtering gas while ions of the sputtered material are rare. Over the last few years, various ionized sputtering techniques have appeared that can achieve a high degree of ionization of the sputtered atoms, often up to 50% but in some cases as much as approximately 90%. This opens a complete new perspective in the engineering and design of new thin film materials. The development and application of magnetron sputtering systems for ionized physical vapor deposition (IPVD) is reviewed. The application of a secondary discharge, inductively coupled plasma magnetron sputtering (ICP-MS) and microwave amplified magnetron sputtering, is discussed as well as the high power impulse magnetron sputtering (HIPIMS), the self-sustained sputtering (SSS) magnetron, and the hollow cathode magnetron (HCM) sputtering discharges. Furthermore, filtered arc-deposition is discussed due to its importance as an IPVD technique. Examples of the importance of the IPVD-techniques for growth of thin films with improved adhesion, improved microstructures, improved coverage of complex shaped substrates, and increased reactivity with higher deposition rate in reactive processes are reviewed.

  • 43. 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)
  • 44. 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.

  • 45. Huang, Shuo
    et al.
    Gudmundsson, Jon Tomas
    Shanghai Jiao Tong University; University of Iceland.
    Ion Energy and Angular Distributions in a Dual-frequency Capacitively Coupled Chlorine Discharge2014In: IEEE Transactions on Plasma Science, ISSN 0093-3813, E-ISSN 1939-9375, Vol. 42, no 10, p. 2854-2855Article in journal (Refereed)
    Abstract [en]

    Ion energy distributions (IEDs) and ion angular distributions (IADs) of Cl2 + and Cl+ ions in a dual-frequency capacitively coupled chlorine discharge are obtained through a particle-in-cell/Monte Carlo simulation. Since the ion transit time is less than the low-frequency period, the ions respond to the instantaneous electric field in the sheath region, which leads to bimodal IEDs for Cl2 + and Cl+ ions. When transiting the sheath, the Cl+ ions experience a more collisional sheath than the Cl2 + ions. The IADs of Cl2 + and Cl+ ions at the surface are almost anisotropic. However, a secondary peak is found in the IAD of Cl+ ions, which can be ascribed to dissociative ionization reactions.

  • 46.
    Huo, Chunqing
    et al.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics. Hainan University, People ’ s Republic of China.
    Lundin, Daniel
    Universite Paris Sud.
    Gudmundsson, Jon Tomas
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics. Université Paris, France; University of Iceland, Iceland.
    Raadu, Michael A.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Bradley, James W.
    University of Liverpool.
    Brenning, Nils
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics. Linköping University, Sweden.
    Particle-balance models for pulsed sputtering magnetrons2017In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 50, no 35, article id 354003Article in journal (Refereed)
    Abstract [en]

    The time-dependent plasma discharge ionization region model (IRM) has been under continuous development during the past decade and used in several studies of the ionization region of high-power impulse magnetron sputtering (HiPIMS) discharges. In the present work, a complete description of the most recent version of the IRM is given, which includes improvements, such as allowing for returning of the working gas atoms from the target, a separate treatment of hot secondary electrons, addition of doubly charged metal ions, etc. To show the general applicability of the IRM, two different HiPIMS discharges are investigated. The first set concerns 400 μs long discharge pulses applied to an Al target in an Ar atmosphere at 1.8 Pa. The second set focuses on 100 μs long discharge pulses applied to a Ti target in an Ar atmosphere at 0.54 Pa, and explores the effects of varying the magnetic field strength. The model results show that -ions contribute negligibly to the production of secondary electrons, while -ions effectively contribute to the production of secondary electrons. Similarly, the model results show that for an argon discharge with Al target the contribution of Al+-ions to the discharge current at the target surface is over 90% at 800 V. However, at 400 V the Al+-ions and Ar+-ions contribute roughly equally to the discharge current in the initial peak, while in the plateau region Ar+-ions contribute to roughly of the current. For high currents the discharge with Al target develops almost pure self-sputter recycling, while the discharge with Ti target exhibits close to a 50/50 combination of self-sputter recycling and working gas-recycling. For a Ti target, a self-sputter yield significantly below unity makes working gas-recycling necessary at high currents. For the discharge with Ti target, a decrease in the B-field strength, resulted in a corresponding stepwise increase in the discharge resistivity.

  • 47.
    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.

  • 48.
    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.

  • 49. Lundin, Daniel
    et al.
    Gudmundsson, Jon Tomas
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    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.
    Minea, Tiberu
    A study of the oxygen dynamics in a reactive Ar/O high power impulse magnetron sputtering discharge using an ionization region model2017In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 121, no 17, article id 171917Article in journal (Refereed)
    Abstract [en]

    The oxygen dynamics in a reactive Ar/O2high power impulse magnetron sputtering discharge hasbeen studied using a new reactive ionization region model. The aim has been to identify thedominating physical and chemical reactions in the plasma and on the surfaces of the reactoraffecting the oxygen plasma chemistry. We explore the temporal evolution of the density of theground state oxygen molecule O2ðX1RgÞ, the singlet metastable oxygen molecules O2ða1DgÞandO2ðb1RgÞ, the oxygen atom in the ground state O(3P), the metastable oxygen atom O(1D), thepositive ions Oþ2and Oþ, and the negative ion O. We furthermore investigate the reaction ratesfor the gain and loss of these species. The density of atomic oxygen increases significantly as wemove from the metal mode to the transition mode, and finally into the compound (poisoned) mode.The main gain rate responsible for the increase is sputtering of atomic oxygen from the oxidizedtarget. Both in the poisoned mode and in the transition mode, sputtering makes up more than 80%of the total gain rate for atomic oxygen. We also investigate the possibility of depositingstoichiometric TiO2in the transition mode.

  • 50. Magnus, Fridrik
    et al.
    Gudmundsson, Jon Tomas
    University of Iceland, Iceland.
    Digital Smoothing of the Langmuir Probe I-V Characteristic2008In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 79, no 7, article id 073503Article in journal (Refereed)
    Abstract [en]

    Electrostatic probes or Langmuir probes are the most common diagnostic tools in plasma discharges. The second derivative of the Langmuir probe I-V characteristic is proportional to the electron energy distribution function. Determining the second derivative accurately requires some method of noise suppression. We compare the Savitzky-Golay filter, the Gaussian filter, and polynomial fitting to the Blackman filter for digitally smoothing simulated and measured I-V characteristics. We find that the Blackman filter achieves the most smoothing with minimal distortion for noisy data.

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