M. Tichý

Academy of Sciences of the Czech Republic, Praha, Praha, Czech Republic

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Publications (143)102.99 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Properties of the plasma plume produced on a bismuth (Bi) target irradiated by a focused extreme-ultraviolet (XUV) capillary-discharge laser beam were investigated. Langmuir probes were used in both single- and double-probe arrangements to determine the electron temperature and the electron density, providing values of 1–3 eV and ~1013–1014 m−3, respectively. Although the temperatures seem to be comparable with values obtained in ablation plasmas produced by conventional, long-wavelength lasers, the density is significantly lower. This finding indicates that the desorption-like phenomena are responsible for the plume formation rather than the ablation processes. A very thin Bi film was prepared on an MgO substrate by pulsed XUV laser deposition. The non-uniform, sub-monolayer character of the deposited bismuth film confirms the Langmuir probe's observation of the desorption-like erosion induced by the XUV laser on the primary Bi target.
    Journal of Physics D Applied Physics 09/2014; 47(40):405205. · 2.53 Impact Factor
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    ABSTRACT: Time-resolved Langmuir probe measurements have been performed in the plume of the 1.5 kW class PPS®1350-ML Hall thruster. The time-dependent electron energy distribution function (EEDF) has been inferred from the probe current–voltage characteristic curves obtained after active stabilization of the discharge. The distribution function changes in the course of time at the breathing oscillation frequency (13.8 kHz). The EEDF is Maxwellian with a depleted tail above the xenon ionization energy whatever the location and the time. The electron density and temperature computed from the EEDF also oscillate at the breathing mode frequency. Experimental outcomes indicate the existence of a low-frequency plasma wave that propagates axially. The wave front speed (2700 m s−1) was found to be compatible with the ion acoustic speed (2300 m s−1).
    Plasma Sources Science and Technology 08/2014; 23(6):065001. · 2.52 Impact Factor
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    ABSTRACT: Growth of Cu nanoparticles in a pulsed gas aggregation cluster source was studied. The cluster growth is enhanced by an energy transport inside the aggregation chamber fed by argon that is delivered in short pulses repeated with low frequency. The effect of pressure, varied during the pulse, on the cluster growth was estimated from time-resolved measurements of mass/size cluster distribution. The cluster mass and the cluster production well correlate with pressure changes. Several stages of cluster growth during the gas-pulse were recognized. Not only larger clusters but also significantly enhanced particle and mass fluxes were observed.
    Physica Status Solidi (A) Applications and Materials 02/2014; · 1.53 Impact Factor
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    ABSTRACT: Formation of Ti–Cu thin films with regard to controlling the copper release is reported in the paper. Copper released from films can inhibit bacterial colonization and can be utilized as an implant surface modification. The copper release has to be controlled (i) to repress the bacteria growth and (ii) to balance the Cu level tolerated by osteoblasts cells. The dual-high power impulsemagnetron sputtering superimposed with mid-frequency discharge was employed for ionized vapor deposition of Ti–Cu films. Itwas found that the microscopical architecture of films is strongly influenced by the pressure during the deposition process. There is an indication that these structural changes are caused by the energy of deposited species (ion distribution functions were measured by time-resolved retarding field analyzer). Grain-like structure with large Cu crystals is formed at higher pressures, i.e. at low ion energies. The grain-like microstructure increases an effective film area which encourages the copper release. It is demonstrated that controlled copper release can be achieved by appropriate setting of the input experimental parameters (pressure, mean discharge current).
    Thin Solid Films 01/2014; 550:389. · 1.87 Impact Factor
  • J Klusoň, P Kudrna, M Tichý
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    ABSTRACT: We present results from two mutually independent measurements of plasma and neutral gas flow velocities in a plasma jet deposition system. Operation of a hollow-cathode discharge within the plasma jet nozzle in the pulse regime enables the simple use of a classical Langmuir probe for the plasma flow velocity measurement. In this method, we assume that the plasma is generated solely inside the nozzle during the power impulse and we measure the time of flight of the ions along a known distance between the nozzle end and the probe. The plasma velocity at the plasma jet axis is then determined by differentiation of the dependence of the distance covered by ions on time. As the second method the well-known Pitot tube is used for measurement of the neutral gas velocity. By comparison of both methods we have experimentally proved that the neutral gas flow velocity is almost unaffected by the presence of the plasma, i.e. it does not substantially depend on whether the discharge is switched on or off. The results of both methods correspond well; detected differences are qualitatively explained. It is documented that the plasma jet can be operated both in a subsonic and in a supersonic regime. We present the dependences of the plasma and neutral gas flow velocity on the distance from the cathode, on the pressure in the reactor chamber, and on the flow rate of the working gas.
    Plasma Sources Science and Technology 12/2013; 22(1):015020. · 2.52 Impact Factor
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    ABSTRACT: The paper focuses on time-resolved diagnostics of unipolar hybrid-dual-High Power Impulse Magnetron Sputtering (hybrid-dual-HiPIMS) discharges. The newly developed sputtering system is based on a combination of dual-HiPIMS with a mid-frequency (MF) discharge. The most important feature of hybrid-dual-HiPIMS systems is the MF pre-ionization which causes/allows: (i) a significant reduction of working pressure by more than one order of magnitude, and (ii) faster ignition and development of HiPIMS pulses. Parameters such as mean electron energy, electron density and electron energy probability function (EEPF) were obtained from time-resolved Langmuir probe diagnostics to demonstrate the aforementioned effects. Calorimetric probe diagnostics were used for determination of the total power density flux. Power flux contributions of particular species, e.g. ions, electrons and neutrals, were estimated as well.
    Vacuum. 04/2013; 90:176–181.
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    ABSTRACT: This article reports on experimental study of the discharge in the low pressure plasma jet sputtering system operated in the continuous DC regime of the discharge excitation. Presented measurements were focused on the description of the working pressure impact on the basic discharge characteristics. The pressure dependence of the gas flow velocity from the nozzle was examined by means of Pitot tube. Further an approximate measurement of the discharge current spatial distribution was realized as well. The second half of the article presents results from Langmuir probe measurements under the conditions of low pressures in the range of units of pascals. These conditions are of special importance in some particular applications especially in preparation of thin layers with high crystallinity. Used experimental setup enabled to perform Langmuir probe diagnostic with spatial resolution both in the plasma jet axis direction and in the direction perpendicular to it (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
    Contributions to Plasma Physics 01/2013; 53(1):10-15. · 0.93 Impact Factor
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    ABSTRACT: Time-resolved measurements of the plasma parameters are performed in the plume of a cross-field discharge. The plasma potential is measured with a cylindrical Langmuir probe and an emissive probe. The electron temperature and density are measured with a cylindrical Langmuir probe. The cross-field discharge is maintained in a harmonic oscillation regime to guarantee reproducible conditions for all measurements (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
    Contributions to Plasma Physics 01/2013; 53(1):63-68. · 0.93 Impact Factor
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    ABSTRACT: The ball-pen probe is an innovative electric probe for direct measurements of plasma potential in magnetised hot plasma. This probe is based on the Katsumata probe concept. The ball-pen probe can adjust the ratio I−sat I+sat of the electron and ion saturation currents to be equal to one causing the ball-pen probe characteristics to become symmetric. If this is achieved, the floating potential of the ball-pen probe is equal to the plasma potential. We show the application of a ball-pen probe in two low-temperature magnetised plasma devices and in torsatron TJ-K (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
    Contributions to Plasma Physics 01/2013; 53(1):39-44. · 0.93 Impact Factor
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    ABSTRACT: This paper reports on an investigation of the hybrid pulsed sputtering source based on the combination of electron cyclotron wave resonance (ECWR) inductively coupled plasma and high power impulse magnetron sputtering (HiPIMS) of a Ti target. The plasma source, operated in an Ar atmosphere at a very low pressure of 0.03 Pa, provides plasma where the major fraction of sputtered particles is ionized. It was found that ECWR assistance increases the electron temperature during the HiPIMS pulse. The discharge current and electron density can achieve their stable maximum 10 μs after the onset of the HiPIMS pulse. Further, a high concentration of double charged Ti++ with energies of up to 160 eV was detected. All of these facts were verified experimentally by time-resolved emission spectroscopy, retarding field analyzer measurement, Langmuir probe, and energy-resolved mass spectrometry.
    Journal of Applied Physics 11/2012; 112:093305-093305-9. · 2.21 Impact Factor
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    ABSTRACT: A Hall thruster (HT) is one type of electric engine currently in use onboard geosynchronous satellites and scientific space probes. In a HT, the electric field at the origin of ion acceleration is generated in a low-pressure magnetized discharge in cross-field configuration. As no grid are employed for beam formation, such a thruster is not current limited and a relatively large thrust, in comparison with gridded ion engines, is achieved, which makes this technology of great interest for orbit transfer maneuvers and deep-space exploration missions. One important issue in the field of electric propulsion is the interaction between the host spacecraft and the plasma plume. Up to now, a large amount of studies has been performed on ion flow properties. Recently we carried out time-averaged measurements of the electron properties in a HT plume by means of Langmuir probe. The goal was to provide accurate data for validation of plume numerical simulations. Nevertheless, as the discharge of a HT is highly non stationary, it appeared necessary to turn to time-resolved measurements. In this contribution we present measurements of the time-varying EEDF at a microsecond time-scale in the plasma plume of two HTs of different sizes and power levels.
    10/2012;
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    ABSTRACT: The electron temperatures Te were measured using a double probe in a premixed methane flame produced by a calibration burner according to Hartung et al. The experiment was performed at atmospheric pressure. In contrast to other authors, we have managed to find typical nonlinearities corresponding to the retarding electron current region and to calculate electron temperatures using a suitable fit on the basis of the measured characteristics. A Pt-Rh thermocouple was used to measure temperatures Th corresponding to “heavy” species. Our results indicate that the flame plasma can be considered to be weakly non-isothermic — Te = (2400–4000) K, Th = (1400–1600) K. On the basis of measurement of the saturated ion current, the number density of the charged particles was estimated at (0.3–3.8) · 1017 m-3. The trends in Te and Th in dependence on the positions of the probes and thermocouple in the flame differ substantially; this fact has not yet been explained (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
    Contributions to Plasma Physics 09/2012; 52(8):692-698. · 0.93 Impact Factor
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    ABSTRACT: Properties of different methods of magnetron sputtering (dc-MS, dual-MS and dual-HiPIMS) are studied and compared with respect to intermetallic Ti-Cu film formation. The quality and features of thin films are strongly influenced by the energy of incoming particles. The ion velocity distribution functions(IVDFs) were measured by time-resolved retarding field analyzer(RFA) in the substrate position. Thin films were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffractometry(XRD) and X-ray reflectometry(XR). Properties and crystallography of Ti-Cu films are discussed as a function of ion energy which is affected by the mode of sputtering. It was found that IVDFsmeasured in pulsed discharges exhibit double-peak distribution. The IVDFs reach the maximum at ion energies about ~8eV. The ion saturated current is highest in dual-HiPIMS discharge (~5μA/cm2) and is mostly represented by Cu+ and Ar+ ions. The mode of sputtering influences chemical composition and film formation. The copper forms polycrystalline fcc-phase while much smaller Ti particles enwraps the copper crystallites or are part of a solid solution.
    The European Physical Journal D 04/2012; 64(2):427-435. · 1.51 Impact Factor
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    ABSTRACT: In a cylindrical magnetron, the electric field is applied in the radial direction and the magnetic field in the axial direction. In this paper, we present a description of a novel construction of cylindrical magnetron developed in the University of Greifswald, FRG. The system has been designed for experimental and computer-modelling studies of the DC discharge in crossed electric and magnetic fields in cylindrical geometry. In order to approach conditions close to an infinitely long system, and hence, to enable a more precise comparison with 1-D simulations, the ratio of the vessel length to the distance between the cathode and the anode has been chosen equal to 20. Six evenly distributed coils create the axial magnetic field. The homogeneity of the magnetic field ±0.2% has been achieved over the whole discharge vessel length 300 mm. The system is equipped with a rotable planar Langmuir probe movable in the radial direction. Measurements of the axial dependencies of plasma parameters are enabled by positioning the Langmuir probe in one of the 5 probe ports located between each couple of coils. We present the results of preliminary measurements of the radial and axial profiles of the plasma density and the mean electron energy.
    Czechoslovak Journal of Physics 04/2012; 50:419-426. · 0.42 Impact Factor
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    ABSTRACT: Highly ionized discharge for physical vapor deposition at very low pressure is presented in the paper. The discharge is generated by electron cyclotron wave resonance (ECWR) which assists with ignition of high power impulse magnetron sputtering (HiPIMS) discharge. The magnetron gun (with Ti target) was built into the single-turn coil RF electrode of the ECWR facility. ECWR assistance provides pre-ionization effect which allows significant reduction of pressure during HiPIMS operation down to p = 0.05 Pa; this is nearly more than an order of magnitude lower than at typical pressure ranges of HiPIMS discharges. We can confirm that nearly all sputtered particles are ionized (only Ti+ and Ti++ peaks are observed in the mass scan spectra). This corresponds well with high plasma density ne ∼ 1018 m−3, measured during the HiPIMS pulse.
    Applied Physics Letters 04/2012; 100(14). · 3.79 Impact Factor
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    ABSTRACT: The present paper is focused on time-resolved diagnostics of the simultaneous combination of dual mid-frequency and dual-high power impulse magnetron sputtering discharges (so-called hybrid-dual-HiPIMS systems). Combined systems are operated with the following parameters – dual-high power impulse magnetron sputtering (fH = 100 Hz, duty cycle 1%) and dual mid-frequency discharge (fM = 94 kHz, duty cycle 30%) – running simultaneously with two magnetron guns. The magnetrons in dual configuration are electrically confined, i.e. electrodes are alternately operated as an anode–cathode (and vice versa) during the sputtering. The dual MF discharge causes a pre-ionization effect which is an important feature because of: (i) a significant reduction of the working pressure by more than one order of magnitude, (ii) an increase of electron and ion energy, and (iii) an increase of the deposition rate. It was found that the ion velocity distribution function (IVDF) during HiPIMS pulses reaches a maximum of about 15–20 eV whereby the dual MF discharge reaches about 0.5–1.5 eV. The time-resolved IVDF measurements revealed that ions with high energy generated at the cathode arrive at the substrate position about 25–30 μs after the HiPIMS pulse ignition. The effect of the hybrid system is illustrated on the deposition of Ti–Cu films. The crystallographic phase and properties of the deposited films are strongly influenced by the energy of incoming particles and by reduced pressure in the chamber.
    Surface and Coatings Technology 02/2012; 206(11–12):2801-2809. · 1.94 Impact Factor
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    ABSTRACT: The far-field plume of a 1.5 kW Hall effect thruster is mapped with a Langmuir probe and an emissive probe. Time-averaged measurements of the plasma potential, the electron temperature and the electron number density are performed for different operating conditions of the thruster. The influence of the discharge voltage, the cathode mass flow rate as well as the magnetic field strength is investigated. The plasma potential decreases from 30 V at 300 mm on the thruster axis to 5 V at 660 mm and at 60°, the electron temperature decreases from 5 to 1.5 eV. The electron number density drops from 3.5 × 1016 to 1 × 1015 m−3 in the far-field plume. The values of the plasma potential and electron temperature measured with the Langmuir probe and the emissive probe are in good agreement.
    Plasma Sources Science and Technology 11/2011; 20(6):065012. · 2.52 Impact Factor
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    ABSTRACT: Time-resolved measurements have been performed during dual High Power Impulse Magnetron Sputtering (dual-HiPIMS) with two cathodes in a closed magnetic field configuration. The effect of a delay between subsequent pulses on electron density, mean electron energy, and ion flux to the substrate was investigated by time-resolved diagnostic methods. Two different delays of 15 µs and 500 µs between subsequent pulses were investigated. The dual-HiPIMS system, operated at a repetition frequency f = 100 Hz and duty cycle of 1 %, was equipped with different metallic targets (Ti, Cu). It is shown that a delay between subsequent pulses influences the plasma parameters and can be used to control deposition processes. It was noted that target surfaces (alternately serving as a cathode/anode) are contaminated by sputtered material from the previous pulse which influences the time-evolution of the discharge parameters (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
    Beiträge aus der Plasmaphysik 03/2011; 51(2‐3):237 - 245.
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    ABSTRACT: Size-controlled Cu clusters are formed in a system which combines pulsed magnetron sputtering and gas condensation at room temperature. The discharge repetition frequency (0.1–25kHz) and the duty cycles (20–90%) of the magnetron sputtering are varied systematically, the influence of discharge current (100–800mA) and the pressure in the condensation tube (25–90Pa) is also investigated. The cluster mass is determined by a quadrupole mass filter in the aggregation tube, and the cluster size by atomic force microscopy (AFM) imaging of deposited clusters. For all preparation conditions, the cluster mass shows a log-normal distribution. A non-monotonic frequency dependence with a maximum at 1kHz and 20% of duty cycle is observed (about 105amu, or cluster diameter 8–10nm). By adjusting discharge frequency and duty cycle, the cluster mass can be decreased by one order of magnitude. We suggest that this effect is caused by energy dissipated into the aggregation tube; and find a critical buffer gas temperature Tg-cr which limits cluster growth. This view is supported by the constant cluster mass flux which does not change on variation of discharge repetition frequency or duty cycle. This feature indicates mass conservation.
    Surface & Coatings Technology - SURF COAT TECH. 01/2011; 205(8):2755-2762.
  • 01/2011: pages P1.059;

Publication Stats

477 Citations
102.99 Total Impact Points

Institutions

  • 2006–2014
    • Academy of Sciences of the Czech Republic
      • Institute of Physics
      Praha, Praha, Czech Republic
  • 1987–2014
    • Charles University in Prague
      • Faculty of Mathematics and Physics
      Praha, Praha, Czech Republic
  • 2001–2010
    • University of Greifswald
      • Institute of Physics
      Greifswald, Mecklenburg-Vorpommern, Germany
  • 2004
    • University of South Bohemia in České Budějovice
      Budejovice, Jihočeský, Czech Republic
  • 1989–1998
    • University of Wales
      • Department of Physics
      Cardiff, Wales, United Kingdom
  • 1993
    • University of Innsbruck
      • Institute for Ion Physics and Applied Physics
      Innsbruck, Tyrol, Austria
  • 1987–1990
    • Université Paris-Sud 11
      Orsay, Île-de-France, France
  • 1979–1987
    • University of Birmingham
      Birmingham, England, United Kingdom