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  • 1
    Electronic Resource
    Electronic Resource
    Effect of collisions on ion dynamics in electron-cyclotron-resonance plasmas (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 1720-1728 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A one-dimensional kinetic code is used to study the effect of ion-neutral (charge exchange and elastic scattering) and ion-ion collisions on plasma flow in the downstream region of an electron-cyclotron-resonance plasma etching system. Ions are assumed to leave the source region at the Bohm velocity. Argon, nitrogen, and CF4 plasmas are simulated, assuming that the dominant ion species are Ar+, N2+, and CF3+, respectively. Results show that charge exchange and elastic scattering collisions play a significant role in reducing the electrostatic potential variation in the downstream region. For neutral gas pressures above ∼1 mTorr, the potential drop in the downstream region is small, which means that most of the energy with which ions hit the substrate surface is gained while crossing the substrate sheath region. Although the effect of ion-ion collisions on the plasma potential profile and on the ion distribution function is weak, ion-ion collisions are responsible for transferring energy from the parallel to the perpendicular direction and hence increasing the perpendicular ion temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351695
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  • 2
    Electronic Resource
    Electronic Resource
    Influence of the high voltage pulse shape on the plasma source ion implantation process (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 2272-2274 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using a two fluid model, we investigate the effects on the ion impact energy, of varying the shape of a large, negative, finite rise time, voltage pulse to a planar target. Two pulse shapes are tested, one with exponential shutoff, and one with a powered linear shutoff. For pulse lengths under 50 μs, we find that pulse shaping can be used to make moderate changes in the energy distribution of the implanted ions. For pulse lengths over 50 μs, there is a negligible difference in the ion impact energy distribution for the pulse shapes tested. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112715
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  • 3
    Electronic Resource
    Electronic Resource
    Two-dimensional fluid simulation of expanding plasma sheaths (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 6967-6973 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The transient sheath expansion around square and cross-shaped targets is simulated numerically with a two-dimensional fluid model. The angular distribution of the ions impinging on the target surface and the nonuniformity of the incident ion dose are calculated. The incident ion dose peaks near, but not at, the convex corner and has a minimum at the concave corner. The dip of the dose profile at the convex corner is shown to be caused by the product of a decreasing normal velocity profile and an increasing ion density profile along the target surface from the center to the corner. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360464
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  • 4
    Electronic Resource
    Electronic Resource
    Dependence of ion-matrix dose on density for planar, cylindrical, and spherical electrodes (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 7616-7618 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ion-matrix dose dependence calculations for plasma source ion implantation in planar, cylindrical, and spherical geometries are presented. It is demonstrated that in the high plasma density limit (in relation to the applied electrode potential and electrode size), the spherical and cylindrical cases approach the planar case. However, in the low relative density limit, the density dependencies diverge with the dependence vanishing for the spherical case, remaining unchanged for the planar case, and with the cylindrical case lying between the previous two. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357928
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  • 5
    Electronic Resource
    Electronic Resource
    Numerical simulation of plasma sheath expansion, with applications to plasma-source ion implantation (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 113-117 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In plasma-source ion implantation a target is pulse biased to a high negative voltage, forming an expanding plasma sheath. A numerical simulation model for the evolution of the sheath has been developed and compared successfully with experimental results. The model is one dimensional (planar, cylindrical, or spherical). The time-dependent, self-consistent potential profile is calculated from Poisson's equation coupled with collisionless fluid equations for the ions and a Boltzmann assumption for the electrons. In addition to the density and potential profile, the simulation yields the ion current to the surface and the energy spectrum of the ions hitting the surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350740
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  • 6
    Electronic Resource
    Electronic Resource
    Drift-cyclotron instability with trapped particle effects in a linear multiple mirror (1985)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 28 (1985), S. 2838-2844 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A drift-cyclotron instability is observed at low magnetic field strengths in a linear multiple mirror. It is characterized by a frequency which decreases with increasing magnetic field strength, propagation in the direction of the electron diamagnetic current, and an azimuthal mode number of 2. The mode is observed when the ion-cyclotron frequency is less than the ion diamagnetic frequency. The frequency is Doppler-shifted by an E×B drift. Effects of particles trapped in the mirror cells alter the characteristics of the instability. The frequency decreases slightly and the fluctuation level increases with increasing mirror ratio for mirror ratios less than 1.1, but then levels off at higher mirror ratios. The drift wave is analyzed by a linear theory which treats finite ion gyroradius, an electron temperature gradient, and trapped electrons. The theory predicts three unstable modes, only one of which is consistent with all of the above measurements. This instability is a Doppler-shifted drift-cyclotron instability modified by trapped particle effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.865203
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  • 7
    Electronic Resource
    Electronic Resource
    Collisionless plasma presheath in a nonuniform magnetic field (1990)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 2 (1990), S. 218-221 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The flow of a collisionless plasma in a nonuniform magnetic field is numerically simulated for a wide range of magnetic field strengths. An iterative scheme for solution of the Vlasov equation and quasineutrality is developed in which a Monte Carlo description for the ion dynamics is used. Ions are launched from distributed sources with finite temperature while electrons are assumed to obey the Boltzmann relation. The dependence of the electrostatic potential profile on both the spatial distribution of the particle source and the magnetic field strength profiles is explicitly investigated. The simulation results are compared with a recently published analytical solution [Phys. Fluids B 1, 725 (1989)].
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.859531
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  • 8
    Electronic Resource
    Electronic Resource
    A collisional model of the plasma presheath (1988)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 31 (1988), S. 1748-1756 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The problem of a collisional plasma flowing into a perfectly absorbing wall has been investigated using a kinetic approach. The plasma is assumed to have a nonzero ion temperature and a Boltzmann distribution of electrons. Ion collisions are included in the analysis through a Bhatnagar–Gross–Krook (BGK) collision term. An equation describing the electrostatic potential variation in the presheath region is derived. This equation is solved numerically for a range of collisionalities. In addition to the potential variation in the presheath, the ion distribution function, the wall potential, and the ion particle and energy fluxes into the sheath are also calculated. The calculation is repeated for three different cases. In the first case ion–neutral collisions are modeled by conserving only particles in the BGK operator. Ion–ion collisions are modeled by conserving particles and momentum in the second case, and by conserving particles, momentum, and energy in the third case. These results give insight into the role of collision conservation laws in describing the plasma flow.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.866663
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  • 9
    Electronic Resource
    Electronic Resource
    Sheath and presheath in a collisionless plasma with a Maxwellian source (1988)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 31 (1988), S. 3645-3648 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Bissell and Johnson [Phys. Fluids 30, 779 (1987)] have calculated the electrostatic potential variation in the sheath and presheath regions of a collisionless plasma in which the source of ions is assumed to be Maxwellian. To do this, they imposed the generalized Bohm criterion as a boundary condition. In this paper the plasma equation is solved numerically without imposing the Bohm criterion as a boundary condition. The results compare well with their results. In addition, the ion distribution function throughout the plasma region is calculated. Because of this particular source model, the ion distribution at the center of the plasma has a spiked non-Maxwellian shape.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.866881
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  • 10
    Electronic Resource
    Electronic Resource
    Observations of a low-frequency mode in a linear multiple mirror (1985)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 28 (1985), S. 2302-2304 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Two drift waves with similar frequencies are observed to be simultaneously unstable under the same plasma parameters. The modes are distinct below a critical magnetic field strength. By varying the mirror ratio and the magnetic field strength the frequencies of the two modes can be made to coalesce. As the critical magnetic field is exceeded the two modes again separate in frequency, but in addition a large-amplitude, low-frequency (〈1 kHz) flute-type mode is also observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.865416
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