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  • 11
    Electronic Resource
    Electronic Resource
    Modeling of the formation of cationic silicon clusters in a remote Ar/H2/SiH4 plasma (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 537-543 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Cationic silicon clusters, containing up to ten silicon atoms, have been measured by mass spectrometry in an argon/hydrogen/silane expanding thermal plasma. A quasi-one-dimensional model, based on the idea that the clustering process initiated by argon or hydrogen ions depends on the path length of the plasma in the deposition chamber and on silane density, is presented. The chemistry is described by ion–molecule reactions between the formed clusters and silane and by dissociative recombination. The model is able to reproduce fairly well the experimental data for various plasma conditions. It is shown that reaction rates for the clustering process do not strongly depend on the number of silicon atoms in the cluster. This result is in contrast with rates published in the previous literature. For the conditions investigated, the consumption of silane by cationic cluster formation is not significant. The contribution of neutral clusters is investigated and recombination proves to be an important process. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373692
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  • 12
    Electronic Resource
    Electronic Resource
    Cavity ring down study of the densities and kinetics of Si and SiH in a remote Ar-H2-SiH4 plasma (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 2065-2073 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Cavity ring down absorption spectroscopy is applied for the detection of Si and SiH radicals in a remote Ar-H2-SiH4 plasma used for high rate deposition of device quality hydrogenated amorphous silicon (a-Si:H). The formation and loss mechanisms of SiH in the plasma are investigated and the relevant plasma chemistry is discussed using a simple one-dimensional model. From the rotational temperature of SiH typical gas temperatures of ∼1500 K are deduced for the plasma, whereas total ground state densities in the range of 1015–1016 m−3 for Si and 1016–1017 m−3 for SiH are observed. It is demonstrated that both Si and SiH have only a minor contribution to a-Si:H film growth of ∼0.2% and ∼2%, respectively. From the reaction mechanisms in combination with optical emission spectroscopy data, it is concluded that Si and SiH radicals initiate the formation of hydrogen deficient polysilane radicals. In this respect, Si and SiH can still have an important effect on the a-Si:H film quality under certain circumstances. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1344911
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  • 13
    Electronic Resource
    Electronic Resource
    Formation of cationic silicon clusters in a remote silane plasma and their contribution to hydrogenated amorphous silicon film growth (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 4029-4039 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The formation of cationic silicon clusters SinHm+ by means of ion–molecule reactions in a remote Ar–H2–SiH4 plasma is studied by a combination of ion mass spectrometry and Langmuir probe measurements. The plasma, used for high growth rate deposition of hydrogenated amorphous silicon (a-Si:H), is based on SiH4 dissociation in a downstream region by a thermal plasma source created Ar–H2 plasma. The electron temperature, ion fluence, and most abundant ion emanating from this plasma source are studied as a function of H2 admixture in the source. The electron temperature obtained is in the range of 0.1–0.3 eV and is too low for electron induced ionization. The formation of silicon containing ions is therefore determined by charge transfer reactions between ions emanating from the plasma source and SiH4. While the ion fluence from the source decreases by about a factor of 40 when a considerable flow of H2 is admixed in the source, the flux of cationic silicon clusters towards the substrate depends only slightly on this H2 flow. This implies a strong dissociative recombination of silicon containing ions with electrons in the downstream region for low H2 flows and it causes the distribution of the cationic silicon clusters with respect to the silicon atoms present in the clusters to be rather independent of H2 admixture. The average cluster size increases, however, strongly with the SiH4 flow for constant plasma source properties. Moreover, it leads to a decrease of the ion beam radius and due to this, to an increase of the ion flux towards the substrate, which is positioned in the center of the beam. Assuming unity sticking probability the contribution of the cationic clusters to the total growth flux of the material is about 6% for the condition in which solar grade a-Si:H is deposited. Although the energy flux towards the film by ion bombardment is limited due to the low electron temperature, the clusters have a very compact structure and very low hydrogen content and can consequently have a considerable impact on film quality. The latter is discussed as well as possible implications for other (remote) SiH4 plasmas. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371324
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  • 14
    Electronic Resource
    Electronic Resource
    Emission spectroscopy on a supersonically expanding argon/silane plasma (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 4156-4163 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Results from emission spectroscopy measurements on an Ar/SiH4 plasma jet which is used for fast deposition of amorphous hydrogenated silicon are presented. The jet is produced by allowing a thermal cascaded arc plasma in argon (I=60 A, V=80 V, Ar flow=60 scc/s and pressure 4 × 104 Pa) to expand to a low pressure (100 Pa) background. In the resulting plasma SiH4 is injected in front of the stationary shock front. Assuming a partial local thermal equilibrium situation for higher excited atomic levels, emission spectroscopy methods yield electron densities (∼ 1018 m−3), electron temperatures (∼5000 K) as well as concentrations of H+, Si+, and Ar+ particles. The emission spectrum of the SiH radical, the A 2Δ–X 2Π electronic transition, is observed. Numerical simulations of this spectrum are performed, resulting in upper limits for the rotational and vibrational temperatures of 4000 and 5600 K, respectively. The results can be understood assuming that, in the expansion, charge exchange and dissociative recombination are dominant processes in the formation of species in excited states, notably Si+.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350850
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  • 15
    Electronic Resource
    Electronic Resource
    Erratum: "Plasma chemistry aspects of a-Si:H deposition using an expanding thermal plasma" [J. Appl. Phys. 84, 2426 (1998)] (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 1243-1243 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369257
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  • 16
    Electronic Resource
    Electronic Resource
    Experimental characterization of a hydrogen/argon cascaded arc plasma source : Proceedings of 5th international conference on ion sources (1994)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 1469-1471 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A H2 /Ar cascaded arc plasma source has been experimentally characterized by determination of the efficiency, the electric field, and the pressure gradient of the arc. The results show that the efficiency of a H2/Ar cascaded arc drops when the hydrogen flow rate is increased. The electron temperature in the argon cascaded arc has been derived to be in the range 9000–12 500 K. For a hydrogen arc, the mass dissociation degree of hydrogen molecules has been derived to be above 60%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1144949
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  • 17
    Electronic Resource
    Electronic Resource
    Influence of molecular processes on the hydrogen atomic system in an expanding argon–hydrogen plasma (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 1002-1008 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An expanding thermal arc plasma in argon–hydrogen is investigated by means of emission spectroscopy. The hydrogen can be added to the argon flow before it enters the thermal arc plasma source, or it can be flushed directly into the vacuum expansion vessel (1–20 vol % H2). The atomic state distribution function for hydrogen, measured at a downstream distance of 20 mm, turns out to be very different in the two cases. For injection in the arc, three-particle recombination is a primary source of hydrogen excitation, whereas measurements with hydrogen injected into the vessel clearly point to a molecular channel (dissociative recombination of formed ArH+) populating atomic hydrogen levels. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871405
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  • 18
    Electronic Resource
    Electronic Resource
    Ion densities in a high-intensity, low flow nitrogen–argon plasma (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 3077-3081 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The plasma density in an expanding thermal plasma was determined using planar Langmuir probe measurements. The arc plasma was operated at low flow (500 standard cm3 per minute). It is shown that the decrease of density with increasing distance from the nozzle of the arc in an argon plasma can be explained by diffusion away from the expansion axis. The determined decay length is 10 cm. In the case that nitrogen is injected in the arc, the plasma density is lowered considerably due to charge exchange and dissociative recombination in the expansion. Because of the low electron density (1017 m−3) at a partial nitrogen flow larger than 10%, the dissociative recombination becomes slow. The main loss process of N2+ ions in this case is diffusion away from the plasma axis. The effective decay length found in the nitrogen plasma is 9 cm. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872442
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  • 19
    Electronic Resource
    Electronic Resource
    Dissociative recombination in cascaded arc generated Ar–N2 and N2 expanding plasma (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 1 (1994), S. 2086-2095 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The expanding plasma obtained from a cascaded arc thermal source is analyzed with double probe, mass spectrometric, and Faraday cup measurements. In the argon–nitrogen mixtures a decrease in ion fluence is observed, contrary to pure argon plasmas in which recombination is insignificant. The recombination in argon–nitrogen plasmas is caused by charge exchange between atomic ions and N2 molecules followed by dissociative recombination. Hence, these processes account for the enhanced axial decay of the plasma density and also for the change in the ion mass spectra of the ion beam extracted from the expanding plasma. The total ion beam current density is also governed by charge exchange followed by dissociative recombination and is thus dependent on the recirculating neutral molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.870604
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  • 20
    Electronic Resource
    Electronic Resource
    Plasma chemistry aspects of a-Si:H deposition using an expanding thermal plasma (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 2426-2435 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The plasma chemistry of an argon/hydrogen expanding thermal arc plasma in interaction with silane injected downstream is analyzed using mass spectrometry. The dissociation mechanism and the consumption of silane are related to the ion and atomic hydrogen fluence emanating from the arc source. It is argued that as a function of hydrogen admixture in the arc, which has a profound decreasing effect on the ion-electron fluence emanating from the arc source, the dissociation mechanism of silane shifts from ion-electron induced dissociation towards atomic hydrogen induced dissociation. The latter case, the hydrogen abstraction of silane, leads to a dominance of the silyl (SiH3) radical whereas the ion-electron induced dissociation mechanism leads to SiHx (x〈3) radicals. In the pure argon case, the consumption of silane is high and approximately two silane molecules are consumed per argon ion-electron pair. It is shown that this is caused by consecutive reactions of radicals SiHx(x〈3) with silane. Almost independent of the plasma conditions used, approximately one H2 is produced per consumedSiH4 molecule. Disilane production is observed which roughly scales with the remaining silane density. Possible production mechanisms for both observations are discussed. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.368977
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