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  • 1
    Electronic Resource
    Electronic Resource
    Temperature dependence of the sticking coefficient of methyl radicals at hydrocarbon film surfaces (2002)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 116 (2002), S. 5125-5136 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The temperature dependence of the interaction of methyl radicals with the surface of a hard, amorphous hydrogenated carbon film is investigated using in situ real-time ellipsometry and infrared spectroscopy. This interaction is considered as an important process during plasma deposition of polymer-like hydrocarbon films or formation of polycrystalline diamond in methane-containing discharges. At room temperature CH3 adsorbs at sp2-coordinated CC bonds at the physical surface of the hard C:H film and forms a completely sp3-hybridized C:H adsorbate with a thickness of ∼0.17 nm. In the following, steady-state film growth is observed with a sticking coefficient of s(CH3)=10−4. At a substrate temperature of T=570 K, incident CH3 causes net erosion with an etching yield of Y(CH3)=10−4. At temperatures above 650 K the sticking coefficient of CH3 becomes positive again, leading to a graphite-like C:H adsorbate. CH3 adsorption is described by a reaction scheme based on the creation of dangling bonds at the film surface via abstraction of surface-bonded hydrogen by incoming CH3 radicals. These dangling bonds act as CH3 adsorption sites at room temperature or as a precursor for chemical erosion at elevated temperature. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1453966
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  • 2
    Electronic Resource
    Electronic Resource
    Simultaneous interaction of methyl radicals and atomic hydrogen with amorphous hydrogenated carbon films (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 2979-2986 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The simultaneous interaction of methyl radicals (CH3) and atomic hydrogen (H) with the surface of amorphous hydrogenated carbon (a-C:H) films is investigated by using quantified radical beam sources. The growth and/or erosion of the films during the interaction of the H and CH3 radical beam with the surface is monitored by means of in situ real-time ellipsometry at a substrate temperature of 320 K. Interaction with the CH3 beam alone results in a slow growth rate corresponding to a sticking coefficient for CH3 of ∼10−4. Simultaneous interaction of an atomic hydrogen beam and the CH3 radical beam with the surface results in a sticking coefficient for CH3 of ∼10−2. A microscopic modeling of this synergistic growth yields a cross section of 3.8 Å2 for CH3 adsorption at a dangling bond, created by abstraction of surface bonded hydrogen due to impinging atomic hydrogen. The cross section for the abstraction of surface bonded hydrogen by impinging CH3 radicals is 1.5×10−3 Å2. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1343894
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  • 3
    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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  • 4
    Electronic Resource
    Electronic Resource
    A combined plasma-surface model for the deposition of C:H films from a methane plasma (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 7718-7727 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356603
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  • 5
    Electronic Resource
    Electronic Resource
    A novel setup for spectroscopic ellipsometry using an acousto-optic tuneable filter (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 3545-3550 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A rotating-analyzer ellipsometer for fast measurements at multiple wavelengths as well as for spectroscopic measurements has been developed. The most important novelty of the setup is the use of an acousto-optic tuneable filter (AOTF) as dispersing element. This offers advantages with respect to the speed of measurement, the adjustment of the intensity of the light, the use of lock-in techniques, and the stability and size of the setup. Advantages and limitations of the use of AOTF's in ellipsometry as well as possible changes in the ellipsometric setup are discussed. The ellipsometer has been mounted on an electron cyclotron resonance plasma deposition chamber. As an example, the deposition of amorphous hydrogenated carbon layers has been studied in situ and are compared to ex situ measurements by variable angle of incidence spectroscopic ellipsometry of the same samples. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145466
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  • 6
    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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  • 7
    Electronic Resource
    Electronic Resource
    Surface loss probabilities of hydrocarbon radicals on amorphous hydrogenated carbon film surfaces (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 2719-2725 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The surface loss probabilities of hydrocarbon radicals on the surface of amorphous hydrogenated carbon (C:H) films are investigated by depositing films inside a cavity with walls made from silicon substrates. This cavity is exposed to a discharge using different hydrocarbon source gases. Particles from the plasma can enter the cavity through a slit. The surface loss probability β is determined by analysis of the deposition profile inside the cavity. This surface loss probability corresponds to the sum of the probabilities of effective sticking on the surface and formation of a nonreactive volatile product via surface reactions. By comparing the deposition profiles measured in CH4, C2H2, C2H4, C2H6 discharges one obtains for C2H radicals β=0.80±0.05, for C2H3 radicals β=0.35±0.1, and for C2H5 radicals β〈10−3. The growth rate of C:H films is, therefore, very sensitive to any contribution of undersaturated C2Hx species in the impinging flux from a hydrocarbon discharge. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372246
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  • 8
    Electronic Resource
    Electronic Resource
    Advantages of the "optical cavity substrate" for real time infrared spectroscopy of plasma–surface interactions (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 4840-4845 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Infrared reflectance spectroscopy can be used to analyze surface reactions during the plasma processing of thin films via the characteristic absorption modes of chemical bonds. However, infrared absorption is a relatively weak effect: to detect a submonolayer quantity of adsorbed or near-surface species in real time, the optical sensitivity must be enhanced in order to produce a measurable reflectance change. This article presents the use of a optically resonant dielectric stack, called an optical cavity substrate, to provide this sensitivity enhancement, and compares this approach quantitatively to other substrate/beam combinations. The optical cavity substrate provides several advantages: (i) a large signal enhancement for both bulk and surface vibrational modes, which is nearly independent of the film refractive index n and thickness up to ∼20 nm, (ii) a large signal enhancement for interfaces buried under thick films, and (iii) a relatively constant baseline signal, which simplifies the data analysis. To demonstrate the power of the optical cavity substrate, we analyze the growth of hydrogenated amorphous silicon in real time. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1456963
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  • 9
    Electronic Resource
    Electronic Resource
    Erratum: "Direct identification of the synergism between methyl radicals and atomic hydrogen during growth of amorphous hydrogenated carbon films" [Appl. Phys. Lett. 76, 676 (2000)] (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 459-459 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.127011
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  • 10
    Electronic Resource
    Electronic Resource
    Direct identification of the synergism between methyl radicals and atomic hydrogen during growth of amorphous hydrogenated carbon films (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 676-678 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The simultaneous interaction of methyl radicals (CH3) and atomic hydrogen (H) with the surface of amorphous hydrogenated carbon (a-C:H) film is investigated. Two identical quantified beam sources for H and CH3 are used. The growth and/or erosion during the simultaneous interaction of the two beams with an amorphous hydrogenated carbon film is monitored by using in situ real-time ellipsometry at a substrate temperature of 320 K. Interaction with the CH3 beam alone causes slow growth, corresponding to a sticking coefficient for CH3 of ∼3×10−5. Simultaneous interaction of the atomic hydrogen beam and the CH3 radical beam yields a sticking coefficient for CH3 of 3×10−3, which is two orders of magnitude larger than for CH3 alone. From a microscopic modeling of this synergistic growth, the reaction probability for CH3 adsorbing at an adsorption site, which is created by atomic hydrogen at the surface, is derived to be 0.14. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.125858
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