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  • 1
    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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  • 2
    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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  • 3
    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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  • 4
    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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  • 5
    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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  • 6
    Electronic Resource
    Electronic Resource
    In situ single wavelength ellipsometry studies of high rate hydrogenated amorphous silicon growth using a remote expanding thermal plasma (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 6388-6394 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An in situ single wavelength HeNe rotating ellipsometry study of high rate (∼80 Å s−1) hydrogenated amorphous silicon (a-Si:H) deposition using an expanding thermal plasma is presented. An optical growth model is used to simulate the measured ellispometric trajectories similar to models used for low rate a-Si:H growth in the literature. The in situ growth at high growth rates was studied as function of the substrate temperature. The refractive index n (at 632.8 nm) increases with increasing temperature corresponding to an increase in the density of the films. The in situ extinction coefficient k (at 632.8 nm) increases with increasing substrate temperature due to a smaller optical band gap and due to an increase in indirect absorption. It is shown that the ellipsometry setup in combination with optical modeling enables us to monitor the surface roughness evolution during deposition and to obtain the dynamic scaling exponent β for postinitial growth. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1321793
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  • 7
    Electronic Resource
    Electronic Resource
    Surface reaction probability during fast deposition of hydrogenated amorphous silicon with a remote silane plasma (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 3313-3320 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The surface reaction probability β in a remote Ar–H2–SiH4 plasma used for high growth rate deposition of hydrogenated amorphous silicon (a-Si:H) has been investigated by a technique proposed by D. A. Doughty et al. [J. Appl. Phys. 67, 6220 (1990)]. Reactive species from the plasma are trapped in a well, created by two substrates with a small slit in the upper substrate. The distribution of amount of film deposited on both substrates yields information on the compound value of the surface reaction probability, which depends on the species entering the well. The surface reaction probability decreases from a value within the range of 0.45–0.50 in a highly dissociated plasma to 0.33±0.05 in a plasma with ∼12% SiH4 depletion. This corresponds to a shift from a plasma with a significant production of silane radicals with a high (surface) reactivity (SiHx,x〈3) to a plasma where SiH3 is dominant. This has also been corroborated by Monte Carlo simulations. The decrease in surface reaction probability is in line with an improving a-Si:H film quality. Furthermore, the influence of the substrate temperature has been investigated. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372342
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  • 8
    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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  • 9
    Electronic Resource
    Electronic Resource
    A combined Thomson–Rayleigh scattering diagnostic using an intensified photodiode array (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 3369-3377 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A combined Thomson–Rayleigh scattering device is discussed. It consists of a Nd:YAG laser as a light source in combination with a multichannel detection technique consisting of a gated light amplifier in combination with an optical multichannel analyzer. Special attention is focused on the analysis of the measured spectra. Including convolution methods and taking into account weak coherent effects increases the dynamic range and the accuracy of the measured electron density ne and temperature Te and neutral particle density n0. Accuracies of 1%–4% for ne, 2%–6% for Te, and 10%–50% for n0 depending on the plasma condition are obtained. The dynamic range for ne is 7×1017–1021 m−3, for n0 is 1020–1023 m−3 and for Te is 1000–50 000 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1142554
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  • 10
    Electronic Resource
    Electronic Resource
    A new absorption spectroscopy setup for the sensitive monitoring of atomic and molecular densities (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 968-974 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: This paper deals with the specifications and the possibilities of a novel highly sensitive optical absorption spectroscopy method. It consists of a cascaded arc as an extremely bright broadband light source with a high resolution spectrometer as a detector. Its interest for a continuous quantitative monitoring of the densities of waste atoms and molecules in the atmosphere is investigated. To this end, theoretical considerations are given with respect to the detection limits and the resolution necessary for selective spectrochemical analysis. In the first measurements with the setup, on a laboratory argon-hydrogen plasma, the versatility and sensitivity of the technique for measuring low species densities is demonstrated. Densities of the sublevels of the argon first excited state, the four Ar(3p54s) metastable and resonant substates, were measured simultaneously in one measuring sequence. The data were analyzed using an efficient line of sight integration technique. The densities of these substates are of the order of 1017 m−3 in a plasma with a pressure of 40 Pa. For the atomic hydrogen H(n=2) state, densities of the order of 1014 m−3 over a length of about 2 cm could be measured, representing a detection limit of approximately 2×1012 m−2. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145631
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