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12 Oct 2009

Volume 95, Issue 15, Articles (15xxxx)

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Appl. Phys. Lett. 95, 153101 (2009); http://dx.doi.org/10.1063/1.3244597 (3 pages)

Geunjae Kwak, Mikyung Lee, Karuppanan Senthil, and Kijung Yong
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CH spectroscopy for carbon chemical erosion analysis in high density low temperature hydrogen plasma

J. Westerhout, N. J. Lopes Cardozo, J. Rapp, and G. J. van Rooij

Appl. Phys. Lett. 95, 151501 (2009); http://dx.doi.org/10.1063/1.3238295 (3 pages) | Cited 11 times

Online Publication Date: 12 October 2009

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The CH A−X molecular band is measured upon seeding the hydrogen plasma in the linear plasma generator Pilot-PSI [electron temperature Te = 0.1–2.5 eV and electron density ne = (0.5–5)×1020 m−3] with methane. Calculated inverse photon efficiencies for these conditions range from 3 up to >106 due to a steeply decreasing electron excitation cross section. The experiments contradict the calculations and show a constant effective inverse photon efficiency of ∼ 100 for Te<1 eV. The discrepancy is explained as the CH A level is populated through dissociative recombination of the molecular ions formed by charge exchange. Collisional de-excitation is observed for ne>5×1020 m−3 and 0.1 eV<Te<1 eV. These results form a framework for in situ carbon erosion measurements in future fusion reactors such as ITER.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
82.30.Fi Ion-molecule, ion-ion, and charge-transfer reactions
52.20.-j Elementary processes in plasmas
82.30.Nr Association, addition, insertion, cluster formation

Very low surface recombination velocity on p-type c-Si by high-rate plasma-deposited aluminum oxide

Pierre Saint-Cast, Daniel Kania, Marc Hofmann, Jan Benick, Jochen Rentsch, and Ralf Preu

Appl. Phys. Lett. 95, 151502 (2009); http://dx.doi.org/10.1063/1.3250157 (3 pages) | Cited 39 times

Online Publication Date: 14 October 2009

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Aluminum oxide layers can provide excellent passivation for lowly and highly doped p-type silicon surfaces. Fixed negative charges induce an accumulation layer at the p-type silicon interface, resulting in very effective field-effect passivation. This paper presents highly negatively charged (Qox = −2.1×1012 cm−2) aluminum oxide layers produced using an inline plasma-enhanced chemical vapor deposition system, leading to very low effective recombination velocities ( ∼ 10 cm s−1) on low-resistivity p-type substrates. A minimum static deposition rate (100 nm min−1) at least one order of magnitude higher than atomic layer deposition was achieved on a large carrier surfaces ( ∼ 1 m2) without significantly reducing the resultant passivation quality.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.25.+i Surface conductivity and carrier phenomena
52.77.Dq Plasma-based ion implantation and deposition
81.65.Rv Passivation
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
72.80.Cw Elemental semiconductors

Neutron yield saturation in plasma focus: A fundamental cause

S. Lee

Appl. Phys. Lett. 95, 151503 (2009); http://dx.doi.org/10.1063/1.3246159 (3 pages) | Cited 13 times

Online Publication Date: 15 October 2009

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Plasma focus research in the direction of fusion energy faces the limitation of observed neutron saturation; the neutron yield Yn falls away from Yn ∼ E02, the scaling deteriorating as storage energy E0 increases toward 1 MJ. Numerical experiments confirm that Yn ∼ E02 applies at low energies and drops to Yn ∼ E00.8 toward 25 MJ; deteriorating already at several hundred kilojoules. We point out that the cause is the dynamic resistance of the axial phase that is constant for all plasma foci. This dynamic resistance dominates the circuit as capacitor bank surge impedance becomes insignificant at large E0, causing current, hence neutron “saturation.”
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52.77.-j Plasma applications

Diagnostic based modeling for determining absolute atomic oxygen densities in atmospheric pressure helium-oxygen plasmas

K. Niemi, S. Reuter, L. M. Graham, J. Waskoenig, and T. Gans

Appl. Phys. Lett. 95, 151504 (2009); http://dx.doi.org/10.1063/1.3242382 (3 pages) | Cited 15 times

Online Publication Date: 15 October 2009

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Absolute atomic oxygen ground state densities in a radio-frequency driven atmospheric pressure plasma jet, operated in a helium-oxygen mixture, are determined using diagnostic based modeling. One-dimensional numerical simulations of the electron dynamics are combined with time integrated optical emission spectroscopy. The population dynamics of the upper O 3p 3P (λ = 844 nm) atomic oxygen state is governed by direct electron impact excitation, dissociative excitation, radiation losses, and collisional induced quenching. Absolute values for atomic oxygen densities are obtained through comparison with the upper Ar 2p1 (λ = 750.4 nm) state. Results for spatial profiles and power variations are presented and show excellent quantitative agreement with independent two-photon laser-induced fluorescence measurements.
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52.70.-m Plasma diagnostic techniques and instrumentation
52.75.-d Plasma devices
52.80.-s Electric discharges
52.65.-y Plasma simulation
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