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  • American Institute of Physics (AIP)  (24)
  • Wiley-Blackwell  (7)
  • American Geophysical Union (AGU)
  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 3833-3837 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Soft carbonized layers prepared in a glow discharge, with a hydrogen concentration of H:C∼4/3, are exposed to helium ion bombardment at energies between 0.3 and 2.6 MeV. A strong ion-induced depletion of up to 3×103 H atoms per incident 4He+ ion is observed by means of high-energy ion beam analysis. The hydrogen release is shown to be a local process, with the electronic energy deposition as the main responsible mechanism. The results are successfully compared to a model which takes into account local bond breaking and retrapping and the local formation of hydrogen molecules.
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  • 2
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 971-973 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Laser-induced fluorescence was applied at the B–X transition of the CH radical to measure absolute densities of the CH radicals in an electron cyclotron resonance methane plasma. The absolute experimental uncertainty is only about 30% due to a new calibration procedure. The CH density correlates well with optical emission from the CH A–X and B–X transitions over a wide pressure range. Experimental results are in satisfactory agreement with predictions from a model based on rate equations for the electron-induced dissociation and ionization of the parent methane gas. This model also includes the interaction of the plasma species with the surrounding walls and the particle transport due to pumping.
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 3401-3403 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A plasma-enhanced chemical vapor deposition process by means of the so-called running discharge has been developed. Amorphous hydrogenated carbon (C:H) films were deposited over a length of 2.5 m on the inner wall of an assembled waveguide system. The average deposition rate from a running discharge in methane was 0.27 A(ring)/s. An increase of the average deposition rate to 2.6 A(ring)/s was achieved using acetylene as process gas, while the H/C ratio in the C:H films remains nearly constant at one. The breakdown of a discharge in the metallic waveguide has been studied in argon plasmas depending on magnetic field, microwave power, and gas pressure. A sharp transition between a magnetically enhanced localized discharge and a running discharge was observed at increasing pressure in the range of some Pascal at a microwave power of 100 W. The running velocity (∼104 m/s) of the plasma package increases with increasing microwave power and increasing gas pressure. This plasma behavior has been further investigated by means of the power balance and plasma modeling in methane.
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1354-1361 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Noncrystalline hydrocarbon films were deposited from methane plasmas in an electron-cyclotron-resonance plasma reactor. The films were characterized by infrared spectroscopy and high-energy ion-beam analysis. Film properties were investigated as a function of the energy of ions impinging on the surface of the growing film. The ion energy was varied by applying a dc bias to the sample in the range from 30 to 200 eV. The ion energy was measured with a retarding field analyzer under identical experimental conditions. An abrupt change was found in the sp3/sp2 ratio in the energy interval from 80 to 120 eV. Other film properties such as the refractive index, density, and hydrogen-to-carbon ratio exhibit a more or less monotonic dependence on the ion energy. The results are compared with published data on hydrocarbon films. An analytical model was developed to describe the energy dependence of the hydrogen fraction in the films. It is based on the assumption that displacement of hydrogen atoms is the dominating mechanism that controls the hydrogen fraction in hydrocarbon films. The results are also discussed on the basis of the fully constrained network model.
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 7718-7727 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The deposition of C:H layers by an electron-cyclotron-resonance plasma from methane was investigated. C:H was deposited at a methane pressure of 1.6 Pa and a substrate temperature between room temperature and 700 K. The film composition, morphology, and structure were investigated by high-energy ion beam analysis and scanning electron microscopy. A combined plasma-surface model for thin-film deposition is proposed, which includes the electron-induced dissociation of methane in the plasma and a growth model. The dominant reactions for film growth are the adsorption of the radical CH3, the direct incorporation of the ions, and the etching reactions with atomic hydrogen from the plasma. A consistent description for the deposition of hydrocarbon layers emerges. It compares favorably with measurements on the temperature dependence of the film growth and the influence of variable gas flow through the reactor on the growth rate and the film morphology.
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3169-3177 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Measurements of the retention of deuterium in polycrystalline nickel were obtained at 193 and 223 K through elastic-recoil detection using a 2.6-MeV 4He beam. The depth profiles so obtained show striking differences with their counterparts measured at higher temperatures. Although the profiles are homogeneous at implanted fluences lower than 3×1018 D+ cm−2, they present a large peak centered slightly deeper than the implantation range at higher fluences. Additional features develop as one further implants. The large peak is associated with the buildup of nickel deuteride. A one-dimensional computer model is developed which partly reproduces the features of the measured depth profiles.
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 1893-1897 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Depth profiles of 10-keV deuterium implanted in nickel were obtained during implantation through elastic recoil detection between 233 and 313 K. The profiles were allowed to reach saturation at each measured temperature. At the lowest temperature, measurements with various implantation fluxes were performed. Aside from surface peaks, the depth profiles show a uniform density of deuterium in the implanted layer and the shape of these profiles is independent of the sample temperature or implantation fluence or flux. The temperature and fluence dependence could be successfully reproduced with a trapping-detrapping model considering three different trap binding energies. Two of the model parameters are in good agreement with previous calculations performed to reproduce reemission measurements.
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 163-168 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Hard amorphous films of a-C:H and a-C:D were deposited by a rf glow discharge in either CH4 or CD4 . By ion bombardment with protons and deuterons, the H/D exchange process was studied as function of the bombardment fluence by means of depth profile measurements. The local hydrogen and deuterium contents are not adding up to a constant "saturation'' value: the local mixing model is not valid. Instead of that an initial depletion appears, which depends on the incident energy of the ions. At higher fluences, the total (H+D):C ratio tends to increase again, due to an increasing influence of the deposition process. This demonstrates a structural difference between a-C:H films and hydrogen-saturated layers of implanted carbon.
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 2068-2072 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Hard amorphous films of a-C:D were deposited by a rf glow discharge in CD4. The implantation of 40-keV 3He+ ions in these films was studied as a function of the helium fluence at temperatures between 100 K and room temperature. The trapped amounts of helium and the deuterium losses in the layer were measured in situ using nuclear reaction analysis with 0.5-MeV D+ and 1-MeV 3He+ beams, respectively, and subsequent ex-situ elastic-recoil detection analysis. A transient helium retention appears in the carbonized layers, occurring only at temperatures below 200 K. Above a critical fluence which depends on temperature and ion flux, outdiffusion of He is observed which is ascribed to the formation of diffusion channels by radiation damage. The deuterium depletion induced by helium bombardment below 200 K sets on in correlation with the helium outdiffusion, but is otherwise independent of the helium trapping.
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 3400-3406 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: On Fe films evaporated on pyrolytic graphite, thick C layers segregate during high-temperature (above about 800 K) light ion irradiation if the penetrating ions are energetic enough to reach the Fe-graphite interface. The thickness of the C segregated layer and the C depth distribution in the Fe film have been determined with 2-MeV 4He+ Rutherford backscattering. A steady-state carbon overlayer is reached at high fluences (above about 1019 particles/cm2), the thickness of which depends on the energy of the irradiating beam for a given thickness of the Fe evaporated film. The anisotropic structure of the pyrolytic graphite substrate influences the thickness of the steady-state C overlayer, thicker C layers being measured for edge-oriented C substrates. Using the Monte Carlo code trim, the production of defects in the graphite substrate has been calculated for different thicknesses of the C overlayer. The total amount of defects produced in the graphite substrate has been identified as the parameter regulating the growth and the steady-state value of the C overlayer. With the depth distributions of defect production generated by trim as source functions, the diffusion of C interstitials in graphite under the influence of recombination with vacancies has been modeled. The segregating C fluxes are identified with the fluxes of interstitials arriving at the Fe/graphite substrate interface for a suitable choice of the parameters in the diffusion equation.
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