Browsing by Author "Gudmundsson, J.T."

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    On singlet metastable states, ion flux and ion energy in single and dual frequency capacitively coupled oxygen discharges
    (Bristol : IOP Publ., 2017) Hannesdottir, H.; Gudmundsson, J.T.
    We apply particle-in-cell simulations with Monte Carlo collisions to study the influence of the singlet metastable states on the ion energy distribution in single and dual frequency capacitively coupled oxygen discharges. For this purpose, the one-dimensional object-oriented particle-in-cell Monte Carlo collision code oopd1 is used, in which the discharge model includes the following nine species: electrons, the neutrals O(3P) and O2(X3 σ-g), the negative ions O-, the positive ions O+ and O, and the metastables O(1D), O2(a1 Δg)and O2(b1 σ+g). Earlier, we have explored the effects of adding the species O2(a1 Δg) and O2(b1 σ+g), and an energy-dependent secondary electron emission yield for oxygen ions and neutrals, to the discharge model. We found that including the two molecular singlet metastable states decreases the ohmic heating and the effective electron temperature in the bulk region (the electronegative core). Here we explore how these metastable states influence dual frequency discharges consisting of a fundamental frequency and the lowest even harmonics. Including or excluding the detachment reactions of the metastables O2(a1 Δg) and O2(b1 σ +g) can shift the peak electron temperature from the grounded to the powered electrode or vice versa, depending on the phase difference of the two applied frequencies. These metastable states can furthermore significantly influence the peak of the ion energy distribution for O-ions bombarding the powered electrode, and hence the average ion energy upon bombardment of the electrode, and lower the ion flux.
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    Target ion and neutral spread in high power impulse magnetron sputtering
    (New York, NY : Inst., 2022) Hajihoseini, H.; Brenning, N.; Rudolph, M.; Raadu, M.A.; Lundin, D.; Fischer, J.; Minea, T. M.; Gudmundsson, J.T.
    In magnetron sputtering, only a fraction of the sputtered target material leaving the ionization region is directed toward the substrate. This fraction may be different for ions and neutrals of the target material as the neutrals and ions can exhibit a different spread as they travel from the target surface toward the substrate. This difference can be significant in high power impulse magnetron sputtering (HiPIMS) where a substantial fraction of the sputtered material is known to be ionized. Geometrical factors or transport parameters that account for the loss of produced film-forming species to the chamber walls are needed for experimental characterization and modeling of the magnetron sputtering discharge. Here, we experimentally determine transport parameters for ions and neutral atoms in a HiPIMS discharge with a titanium target for various magnet configurations. Transport parameters are determined to a typical substrate, with the same diameter (100 mm) as the cathode target, and located at a distance 70 mm from the target surface. As the magnet configuration and/or the discharge current are changed, the transport parameter for neutral atoms ζ tn remains roughly the same, while transport parameters for ions ζ ti vary greatly. Furthermore, the relative ion-to-neutral transport factors, ζ ti / ζ tn, that describe the relative deposited fractions of target material ions and neutrals onto the substrate, are determined to be in the range from 0.4 to 1.1.