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  • 1
    Electronic Resource
    Electronic Resource
    Determination of the absolute CH3 radical flux emanating from a methane electron cyclotron resonance plasma (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 31-33 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Methyl radicals from a methane electron cyclotron resonance plasma are measured quantitatively at the sample position by ionization-threshold mass spectrometry (ITMS). The absolute fluxes are determined by calibrating the CH3 ITMS results with those of methane, taking into account the published energy-dependent cross sections for the ionization of CH3 and CH4, respectively. The measured CH3 radical fluxes are on the order of some 1015 cm−2 s−1, which is in accordance with recent modeling results. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.121713
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  • 2
    Electronic Resource
    Electronic Resource
    Growth and erosion of hydrocarbon films investigated by in situ ellipsometry (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 1092-1098 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The growth of hydrocarbon films (C:H films) from a methane plasma and their erosion by a hydrogen plasma are investigated by means of in situ ellipsometry. The kinetic energy of the ions impinging on the surface during deposition and erosion is varied by applying a rf bias resulting in a dc self-bias ranging from floating potential up to 100 V. In addition, the substrate temperature is varied from room temperature up to 600 K. The direct comparison between the growth and erosion indicates that the temperature dependence of the growth rate during deposition from a methane plasma is caused by the temperature-dependent erosion due to reactions with the abundant atomic hydrogen. Furthermore, the synergistic effects between hydrogen ions and atomic hydrogen on the etch rate of C:H films are investigated. The underlying surface reactions during the erosion show up in the optical response of the deposited films as measured by ellipsometry. These results are compared with findings in the literature on the elementary steps of the erosion of C:H films by atomic hydrogen. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360796
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  • 3
    Electronic Resource
    Electronic Resource
    Transport and structural modification during nitrogen implantation of hard amorphous carbon films (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 5185-5194 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Hard amorphous carbon (ta-C) films were implanted with 20 keV N+ ions with different fluences up to 6×1017/cm2 at different substrate temperatures. The nitrogen content of the films was monitored in situ using elastic recoil detection analysis. A characteristic temperature dependence is observed for the maximum achievable [N]/[C] composition ratio, with a drop of the saturation level from the room-temperature value of 0.35 to 0.17–0.12 above 150 °C. It is shown that the higher nitrogen retention at room temperature is correlated with the formation of N2-containing gas bubbles which are not present in samples implanted with high fluences at elevated temperatures. From residual-gas analyses it is found that nitrogen is reemitted from the films mainly as N2 when saturation occurs. Double-implantation experiments with spatially separated 14N and 15N implanted regions, respectively, indicate that the N–N molecule recombination observed at large implantation fluences occurs inside the films and not at the surface. Significant changes of the microstructure of the films are found with increasing implantation fluences. Inside the implanted near-surface region of several 10 nm thickness the density of the material decreases from 3.0 to about 1.7 g/cm−3. Graphitic clusters are identified in samples implanted up to saturation at 400 °C, using cross-section transmission electron microscopy. A basic approach to modeling the nitrogen saturation and release at large fluences is presented. Both nitrogen release and structural modification processes are interpreted as a tendency towards thermodynamic equilibrium which may constitute a strong driving force against the synthesis of nitrogen-rich hard C:N materials, compared to other nitride phases. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367338
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  • 4
    Electronic Resource
    Electronic Resource
    The transition of a multipactor to a low-pressure gas discharge (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 940-944 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Multipactor discharges can cause severe problems in high voltage rf systems like rf antennae or transmission lines of ion cyclotron resonance heating (ICRH) in nuclear fusion devices, where they may initiate gas breakdown. To study this eventual transition from a starting multipactor into an ordinary rf discharge detailed investigations were performed using a parallel plate geometry, 50 MHz operating frequency and up to one kilovolt rf amplitude. Measurements of electric data (rf amplitude, absorbed and reflected power, discharge current), electronic parameters (electron current density and energy distribution) and light emission were used for characterization. As a main result a new type of well defined discharge regime was identified, which seems important for the transition from multipactor into gas breakdown in rf devices. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872564
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  • 5
    Electronic Resource
    Electronic Resource
    Plasma chemical vapor deposition of hydrocarbon films: The influence of hydrocarbon source gas on the film properties (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 3988-3996 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Hydrocarbon films were prepared by electron cyclotron resonance plasma deposition from different hydrocarbon source gases at varying ion energies. The source gases used were the saturated hydrocarbons CH4, C2H6, C3H8, C4H10 (n- and iso-) and the unsaturated hydrocarbons C2H4 and C2H2 as well as mixtures of these gases with hydrogen. Film deposition was analyzed in situ by real-time ellipsometry, and the resulting films ex situ by ion-beam analysis. On the basis of the large range of deposition parameters investigated, the correlation between hydrocarbon source gas, deposition parameters, and film properties was determined. The film properties are found to be influenced over a wide range not only by the energy of the impinging ions, but also by the choice of source gas. This is in contrast to a widely accepted study where no dependence of the film properties on the source gas was observed, this being ascribed to a "lost-memory effect." A strong correlation was found between the hydrogen content of the films and the film properties. This strong correlation is explained on the basis of the random-covalent-network model. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371318
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  • 6
    Electronic Resource
    Electronic Resource
    Experimental determination of the absorption strength of C–H vibrations for infrared analysis of hydrogenated carbon films (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 475-477 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Plasma-deposited, hydrogenated carbon thin films were investigated by infrared analysis and high-energy ion analysis. The absolute quantities of hydrogen in the films, as measured by ion beam analysis, and the strength of the C–H vibrational bands around 3000 cm−1 were compared to determine the average absorption strength for these bands. The absorption strength was found to vary by a factor of 4 depending on the structure of the hydrocarbon films. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116418
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  • 7
    Electronic Resource
    Electronic Resource
    Hydrogen bonding in plasma-deposited amorphous hydrogenated boron films (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 1905-1908 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Hydrogenated amorphous boron (a-B:H) thin films were prepared by radio-frequency plasma deposition using B2H6 (10%) in H2 as precursor gas. The influence of the substrate temperature and self-bias on the a-B:H film structure was investigated. The boron and hydrogen atom densities were determined by ion-beam analysis. The film structure, especially the bonding of hydrogen to boron, was investigated by Fourier transform infrared (FTIR) spectroscopy. The FTIR data were quantified by using a new formalism which allows a proper calculation of the extinction coefficient from the FTIR spectra. The intensities of the different boron-hydrogen absorption bands were compared with the ion-beam analyzed hydrogen atom densities to determine the absorption strength of the B–H terminal and B–H–B bridge bonds. A non-negligible fraction of hydrogen is shown to be bonded to boron in a B–H–B bridge bond. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.365997
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  • 8
    Electronic Resource
    Electronic Resource
    Surface relaxation during plasma-enhanced chemical vapor deposition of hydrocarbon films, investigated by in situ ellipsometry (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 1531-1535 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The ion–thin-film interaction during plasma-enhanced chemical vapor deposition of hydrocarbon films (C:H films) from a methane electron cyclotron resonance plasma was investigated by means of in situ ellipsometry. Films were deposited with varying rf bias, resulting in a dc self-bias ranging from floating potential up to 100 V. The ion bombardment during plasma-enhanced chemical vapor deposition of hydrocarbon films leads to a disturbed surface layer, which becomes apparent in the in situ ellipsometric results by optical constants which are higher than those for the bulk material. The optical constants of the modified surface layer increase with ion energy during deposition, but decrease with the addition of hydrogen to the source gas. When using acetylene instead of methane for the deposition we also find a higher value for the optical constants. After switching off the plasma, the increased optical constants of the surface layer relax to its equilibrium state. The sources of this modified film surface and the mechanisms for its relaxation are discussed in this article. The change of the optical constants of the film surface is compared to the dependence of the film properties on the gas composition and the ion bombardment during deposition. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.364184
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  • 9
    Electronic Resource
    Electronic Resource
    On the presence of molecular nitrogen in nitrogen-implanted amorphous carbon (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 1387-1389 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Hard amorphous carbon (ta-C) films were implanted with 20 keV N+ ions into saturation at two different temperatures. Monitoring the composition ratio [N]/[C] using in situ elastic recoil detection analysis, saturation levels [N]/[C] of 0.35 and 0.16 have been found for implantations at room temperature and 400 °C, respectively. Raman and x-ray photoelectron spectroscopy analyses of the implanted films indicate the presence of N2 molecules inside room-temperature implanted samples, but not for the case of implantation at 400 °C. Cross-section transmission electron microscopy images show the presence of near-surface voids, interpreted as remnants of N2-filled bubbles, in the former case. Annealing experiments show that about 50% of the total N inventory consists of nitrogen only weakly trapped inside the carbon matrix in room-temperature implanted films, this fraction being significantly reduced in samples held at 400 °C during implantation. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.118585
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  • 10
    Electronic Resource
    Electronic Resource
    Role of hydrogen ions in plasma-enhanced chemical vapor deposition of hydrocarbon films, investigated by in situ ellipsometry (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 1322-1324 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ion bombardment during plasma-enhanced chemical vapor deposition of hydrocarbon films mainly governs the properties of the films. The range of this ion-induced modification of the optical properties of hydrocarbon films was determined in situ by monochromatic ellipsometry. The hydrocarbon films were deposited by an electron cyclotron resonance methane plasma onto silicon substrates and additional rf bias was applied to vary the kinetic energy of the impinging ions. The ion-induced modification of the film properties was investigated by means of a double layer consisting of a polymerlike film with low optical absorption and a hard carbon film with high absorption on top. The deposition of this double layer was monitored in situ by ellipsometry during the growth and during the erosion of this film system in an oxygen plasma at floating potential. From these data it is possible to determine with high accuracy the range of the ion-induced modification of the optical properties. This layer ranges from 6 A(ring) at 30 V dc self-bias to 40 A(ring) at 100 V dc self-bias, which is consistent with TRIM.SP calculations for the bombardment of polymerlike films by hydrogen ions. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113229
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