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Plasma Science, IEEE Transactions on

Issue 11 • Date Nov. 2010

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Displaying Results 1 - 19 of 19
  • Table of contents

    Publication Year: 2010 , Page(s): C1
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  • IEEE Transactions on Plasma Science publication information

    Publication Year: 2010 , Page(s): C2
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  • Special Issue on HiPIMS and High Power Glow Discharge

    Publication Year: 2010 , Page(s): 3005 - 3006
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  • Plasma Parameters in a Pre-Ionized HiPIMS Discharge Operating at Low Pressure

    Publication Year: 2010 , Page(s): 3007 - 3015
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    A high power impulse magnetron sputtering (HiPIMS) discharge assisted by a dc pre-ionizer operating at low pressure has been investigated using the Langmuir probe technique as well as energy-resolved mass spectrometry. It was found that the background plasma with densities of about 1 × 109 cm-3 provided by the dc pre-ionizer can reduce the ignition delay time of the HiPIMS plasma from more than 50 μs to less than 5 μs at a working pressure of about 0.1 Pa. Furthermore, the technique of super-imposing HiPIMS with the dc discharge can be readily employed with a low self-sputtering yield target (Ti) at a working pressure of 0.08 Pa, with a pulse width and a repetition frequency of 100 μs and 100 Hz, respectively. This leads to a power density of 450 Won 2 at the target. At these operating conditions, the probe measurements showed a high-density plasma 6 cm in front of the target. The maximum electron density was found to be 8 × 1011 cm-3, with an effective electron temperature of about 3-4 eV. A study of the ion mass distribution revealed that the intensity of Ti2+ ions is larger than the peak of Ti+ in low-pressure operation. Moreover, the number of metal ions in the high-energy tail of the ion energy distribution function increased with a decreasing pressure from 0.5 to 0.08 Pa. View full abstract»

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  • High-Power Pulsed Magnetron Sputtering Glow Plasma in Argon Gas and Pulsed Ion Extraction

    Publication Year: 2010 , Page(s): 3016 - 3027
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (629 KB) |  | HTML iconHTML  

    Plasma-ion processing enhances the functionality of a film, and as such, metal plasma sources are indispensable in film preparation. A magnetron sputtering glow plasma is generated by a pulsed power source in a process called a high-power pulsed magnetron sputtering glow plasma. Metal species are sputtered by energetic argon ions and are ionized. Ions are extracted from the plasma when a substrate holder electrode (SHE) is immersed in the plasma. This process has been referred to as plasma-based ion implantation and deposition (PBII&D). This paper deals with the electrical and optical characteristics of a pulsed magnetron sputtering glow plasma in which pulsed ion extraction is carried out by the PBII&D method. Work is presented showing that the voltage and current characteristics can be represented as a series connection of voltage source, current-limiting resistor, and plasma impedance. As a result, the characteristics are normalized by the peak current and the maximum power consumed in the plasma where a circuit-matching condition is satisfied. However, when the temporary behavior of the current changes by over 20 A/μs under the experimental conditions, a circuit inductance originating from the connecting wire in the circuit can significantly influence the electrical characteristics. As a result, the peak current and the maximum consumed power cannot be used to normalize the electrical characteristics. When an inductive component is considered, the electrical characteristics obtained experimentally are curve fitted to the calculated values. Ion extraction from the glow plasma was successfully observed. This suggests that the PBII&D method can be employed in the case of a high-power pulsed glow plasma. The waveform of the extracted ion current is seen to have a sharp peak at the initial stage of voltage application to the SHE, followed by a stationary state. This confirms that the SHE is immersed in the plasma. The plasma density is on the o- - rder of 1017 m-3 and is estimated by the recovery characteristics of the voltage applied to the SHE. The ion density of the glow plasma is found to be proportional to the extracted stationary ion current at the end of the pulse applied to the SHE. The temporary behavior of the optical emission spectrum of the glow plasma confirms that sputtered titanium species are ionized to a singly ionized state and that their appearance is delayed from the appearance of argon ions. View full abstract»

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  • Origin of the Delayed Current Onset in High-Power Impulse Magnetron Sputtering

    Publication Year: 2010 , Page(s): 3028 - 3034
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    Repetitive pulses of voltage and current are applied in high-power impulse magnetron sputtering. The current pulse usually lags the applied voltage by a significant time, which, in some cases, can reach several tens of microseconds. The current time lag is generally highly reproducible and jitters less than 1% of the delay time. This work investigates the time lag experimentally and theoretically. The experiments include several different target and gas combinations, voltage and current amplitudes, gas pressures, pulse repetition rates, and pulse durations. It is shown that, in all cases, the inverse delay is approximately proportional to the applied voltage, where the proportionality factor depends on the combination of materials and the conditions selected. The proportionality factor contains the parameters of ionization and secondary-electron emission. The statistical time lag is negligible, while the formative time lag is large and usually dominated by ion motion (inertia), although, at a low pressure, the long free path of magnetized electrons causing ionization contributes to the delay. View full abstract»

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  • Time- and Species-Resolved Plasma Imaging as a New Diagnostic Approach for HiPIMS Discharge Characterization

    Publication Year: 2010 , Page(s): 3035 - 3039
    Cited by:  Papers (1)
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (361 KB)  

    We present a novel approach in fast imaging of high-power impulse magnetron sputtering (HiPIMS) discharges in which bandpass optical interference filters are used to isolate the optical emission signal originating from different species populating the plasma. In this paper, we describe the methodology of the proposed diagnostics and discuss its application. In particular, we demonstrate the use of this technique for the time-resolved analysis of HiPIMS discharges operated with a chromium cathode in argon at 4 Pa. Two optical filters were designed and fabricated: (i) one for neutral chromium emission lines (400-540 nm); and (ii) the other one for neutral working gas emission lines and bands (above 750 nm). The introduction of such filters is used to distinguish different phases of the discharge and to reveal numerous plasma effects including background gas excitations during the discharge ignition, gas shock waves, and expansion of metal-rich plasmas. View full abstract»

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  • Influence of Substrate Biasing on (Al, Ti)N Thin Films Deposited by a Hybrid HiPIMS/DC Sputtering Process

    Publication Year: 2010 , Page(s): 3040 - 3045
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    (Al, Ti)N coatings were reactively cosputtered using a hybrid process in Ar/ N2 atmosphere, where aluminum and titanium targets were supplied via classical pulsed-dc and HiPIMS power units, respectively. Aiming to study the influence of substrate biasing on the properties of the coatings, all other parameters were kept constant. Unexpectedly, the titanium content seems to remain unchanged, whereas the deposition rate, the morphology, the structure, and the mechanical properties of the coatings strongly depend on the applied voltage on the samples. Increasing the negative bias voltage leads to a slight decrease in the deposition rate of up to -100 V, and for a higher bias voltage, the deposition rate drops drastically. The compressive stresses show similar evolution. These behaviors depend on the attraction of highly energetic metallic and Ar+ ions, which strongly impinge the biased substrates. Finally, all the films synthesized below a negative bias of -100 V are crystallized in hcp-AIN form, whereas those deposited above -130 V exhibit the c-TiN structure. This induces a hardness enhancement, but combined to poor adhesion due to a too high level of internal stresses, this induces the characteristic of a brittle and rigid character. View full abstract»

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  • \hbox {CrN}_{\rm x} Films Prepared by DC Magnetron Sputtering and High-Power Pulsed Magnetron Sputtering: A Comparative Study

    Publication Year: 2010 , Page(s): 3046 - 3056
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    CrNx (0 ≤ x ≤ 0.91) films synthesized using high-power pulsed magnetron sputtering, also known as high-power impulse magnetron sputtering (HiPIMS), have been compared with those made by conventional direct-current (dc) magnetron sputtering (DCMS) operated at the same average power. The HiPIMS deposition rate relative to the DCMS rate was found to decrease linearly with increasing emission strength from the Cr ions relative to Cr neutrals, in agreement with the predictions of the target-pathway model. The low deposition rate in HiPIMS is thus a direct consequence of the high ionization level (~56%) of the target material and effective capturing of Cr ions by the cathode potential. Although the HiPIMS deposition rate did not exceed 40% of the DCMS rate, the drop in the relative deposition rate upon increasing the N2-to-Ar flow ratio, fN2/Ar, was found to be similar for both sputtering techniques. Films prepared by HiPIMS contained similar amounts of atomic nitrogen as the dc-sputtered samples grown at the same fN2/Ar indicating that the nitride formation at the substrate takes place mostly during the time period of the high-power pulses, and the N2 uptake between the pulses is negligible. The microstructure evolution in the two types of CrNx films, however, differed clearly from each other. A combination of a high substrate bias and a high flux of doubly charged Cr ions present during the HiPIMS discharge led to a disruption of the grain growth and renucleation, which resulted in column-free films with nanosized grains not observed in the conventional DCMS-based process. The comparison of nanoindentation hardness as a function of fN2/Ar revealed superior properties of HiPIMS-sputtered films in the entire range of gas compositions. View full abstract»

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  • A Comparison of Thin Silver Films Grown Onto Zinc Oxide via Conventional Magnetron Sputtering and HiPIMS Deposition

    Publication Year: 2010 , Page(s): 3057 - 3061
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    Silver coatings are commonly deposited via dc magnetron sputtering for use in a variety of applications that require high transparency to visible light and good electrical conductivity, including, for example, low-emissivity coatings. The films need to be fully dense in order to achieve the correct optical and electrical properties, although the typical growth mechanism for silver films is by the nucleation and coalescence of islandlike structures that can result in the generation of voids within the coating and uneven surface topography. As a consequence, in order to achieve acceptable electrical properties, the optical transparency of the silver coating is often compromised due to the excessive film thicknesses required for continuous electrically conductive layers. Conventional methods used to enhance the adatom mobility, hence increasing the density of the coatings, include the application of an electrical bias to the substrate or substrate heating, both of which can be problematic for large-area dielectric substrates such as float glass or polymer web. One alternative is the production of a coating using a deposition flux with a high fraction of ionization. This can be achieved via high-power impulse magnetron sputtering (HiPIMS), leading to an enhanced delivery of energy to the adatoms via recombination at the substrate surface. Thin films of silver were deposited onto zinc oxide-coated glass substrates via continuous dc and pulsed-dc magnetron sputtering and also via HiPIMS at the same time-averaged power in order to compare the structure and growth mechanisms via techniques, including AFM, XRD, and Hall-effect measurements for the electrical characterization. View full abstract»

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  • Properties of TiAlCN/VCN Nanoscale Multilayer Coatings Deposited by Mixed High-Power Impulse Magnetron Sputtering (HiPIMS) and Unbalanced Magnetron Sputtering Processes—Impact of HiPIMS During Coating

    Publication Year: 2010 , Page(s): 3062 - 3070
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (784 KB) |  | HTML iconHTML  

    Nanoscale multilayer TiAlCN/VCN coating has been deposited by pure unbalanced magnetron sputtering (UBM) and high-power impulse magnetron sputtering (HiPIMS)-UBM techniques. The V+ HiPIMS etching used in both processes has shown excellent adhesion (Lc > 50) of the coating to the substrate. The plasma compositional analysis of V+ HiPIMS etching has shown high metal-to-gas ion ratio with ionization states of V up to 5+. Moreover, during the coating of TiAlCN/VCN, the plasma analysis has confirmed the higher production rate of metal ions in the case of HiPIMS-UBM in contrast to pure UBM. This has resulted to a denser closed columnar microstructure of the coating during the HiPIMS-UBM technique than UBM. A thermogravimetric analysis has shown increased oxidation-resistance temperature for coatings deposited by HiPIMS-UBM (w780°C) with significantly lower mass gain. The scanning electron microscope and X-ray diffraction studies of the oxidized surface of the coating have revealed the formation of lubricant Magneli phase oxides of V2O5 and TiO2 at elevated temperature. The wear coefficient of the coating deposited by HiPIMS-UBM has shown two orders of magnitude lower value than that for the UBM-deposited coatings, which represents significant advantage for coatings deposited by UBM. This enhanced performance in oxidation-resistance dry sliding wear conditions can be attributed to the extremely dense structure of the HiPIMS coatings, which could be promising in elevated temperature applications. View full abstract»

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  • Effect of Negative Substrate Bias on the Structure and Properties of Ta Coatings Deposited Using Modulated Pulse Power Magnetron Sputtering

    Publication Year: 2010 , Page(s): 3071 - 3078
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    Crystalline phase control is critical for obtaining desired structure and properties of Ta coatings deposited by magnetron sputtering. We have shown the approach to control the alpha and beta Ta phase formations by tuning the negative substrate bias voltage during modulated pulse power (MPP) magnetron sputtering, which generates a large fraction of target metallic ions in the plasma providing enhanced ion bombardment on the growing film. It was found that the peak and mean substrate ion current densities increased rapidly from 42 to 165 mAcm-2 and 16 to 55 mAcm-2, respectively, as the negative substrate bias voltage was increased from -20 to -50 V and became saturated with a further increase in the negative substrate bias voltage. As the negative substrate bias voltage was increased from 0 to -100 V, the MPP Ta phase changed from an all beta phase when the bias voltage was at 0 V and a floating bias, to a mixed alpha and beta phases when the bias voltage was in the range of -30 to -40 V, and finally to an all alpha phase when the negative bias voltage was -50 V or greater. In this paper, alpha Ta coating with thicknesses up to 100 μm were successfully deposited using the MPP technique with high deposition rate. The residual stress of the thick Ta coating was measured using an X-ray stress analyzer. The adhesion strength of the thick Ta coating was evaluated using Rockwell-C indentation and scratch tests. The possibility to coat complex-shaped substrates with good coating coverage on the substrate's surface placed orthogonal to the target has also been demonstrated. View full abstract»

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  • XPS Study on Chemical State and Phase Structure of PBII Nitriding M50 Steel

    Publication Year: 2010 , Page(s): 3079 - 3082
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    X-ray diffraction (XRD) and X-ray photoelectron spectroscopy were used to study the structure and the element chemical states of plasma-based ion implantation (PBII) nitriding M50 steel. An ~70-nm-thick oxygen-rich layer was formed in the surface after PBII treatment, where C and V elements were absent, Cr and Mo elements were in the manner of oxide, and Fe element was in the manner of Fe3O4 and iron nitride. XRD patterns revealed that the Fe16N2 phase was formed in the subsurface of the nitrided layer. Four different chemical states of nitrogen with binding energies of 404.1, 399.2, 396.7, and 394.3 eV were found in sequence with sputtering time increasing, which were confirmed to belong to NO bonding, Fe3(N, O) [or Fe4(NO)], Fe3N (or Fe4N), and Fe16N2. View full abstract»

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  • A Specially Designed PLC-Based High-Voltage Pulse Modulator for Plasma Immersion Ion Implantation

    Publication Year: 2010 , Page(s): 3083 - 3088
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (693 KB) |  | HTML iconHTML  

    A novel high-voltage pulse power system based on a programmable logic controller (PLC) is developed for plasma immersion ion implantation (PIII). The PLC unit with strong anti-interference ability is utilized to optimize both electrical parameters and ion-implantation processes with manual or/and procedure modes. Specially designed periphery circuits are developed to realize the arbitrary adjustment of pulsing frequency and width which is impossible for conventional PLC systems. The electrical protection can also work rapidly in the case of a sudden short circuit. In the main power circuit, a tetrode hard tube is employed to switch the dc high voltage. In order to reduce the rise time of the pulse as much as possible, the potentials on the tetrode grids are optimized. A closed-loop system is also designed to ensure implantation voltage not to depend on the plasma load during the PIII processes. With the help of numerical calculation or simulation, the expected ion energy-number spectrum can be easily obtained. View full abstract»

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  • HiPIMS Ion Energy Distribution Measurements in Reactive Mode

    Publication Year: 2010 , Page(s): 3089 - 3094
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    In this paper, mass spectrometry was used to measure the ion energy distributions of the main species during the sputtering of an aluminum target in a reactive Ar + N2 mixture. Both conventional magnetron sputtering (dc) and high-power impulse magnetron sputtering (HiPIMS) were used. It appears that, in the HiPIMS, N+ and Al+ ions are significantly more energetic (up to 70 eV) than in the dc (<;40 eV). Furthermore, the HiPIMS Al+ signal is two orders of magnitude greater than in the dc, and time-resolved measurements indicate that most of the ion flux hits the substrate during the OFF time of the impulse sequence. View full abstract»

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    Publication Year: 2010 , Page(s): 3095
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    Publication Year: 2010 , Page(s): 3096
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  • IEEE Transactions on Plasma Science information for authors

    Publication Year: 2010 , Page(s): C3
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    Publication Year: 2010 , Page(s): C4
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