In this work, the deposition of tungsten (W) films by High Power Impulse Magnetron Sputtering (HiPIMS) has been investigated. By adopting a combined modeling and experimental approach, the role of ...magnetic field strength and bias configuration on growth of W films has been studied since they are relevant parameters for the energetic and ionized HiPIMS environment. Modeling results showed that increasing the magnetic strength from 40 to 60 mT led to larger W ion fraction in the plasma and, contemporary, to higher ion back-attraction to the target. This, in turn, resulted in a similar W ion fraction in the flux towards the substrate for the two magnetic field strengths considered during the on-time of the voltage pulse. On the contrary, the W ion fraction became significantly different in the afterglow and the same happened to the ion flux composition. Exploiting the studied discharges, W films have been grown applying at substrate negative pulsed bias voltages, both synchronized and delayed to the voltage pulse onset. Films morphology, microstructure, residual stress, composition and density have been examined. In light of plasma differences retrieved from the numerical investigation, film growth and properties are discussed.
•Combined modeling of HiPIMS W/Ar plasma and experimental characterization of grown W films•Magnetic field determines composition and evolution of the ion flux coming from Ar/W plasma.•The effect of bias voltage amplitude on W film features strongly depends on its delay with respect to voltage pulse onset.
MCPlas is introduced as a powerful tool for automated fluid model generation with application to the analysis of dielectric barrier discharges (DBDs) operating in different regimes. MCPlas consists ...of a number of Matlab scripts and uses the COMSOL Multiphysics module LiveLink for MATLAB to build up equation-based COMSOL Multiphysics models from scratch. The present contribution highlights how MCPlas is used to implement time-dependent models for nonthermal plasmas in spatially one-dimensional (1-D) and axisymmetric two-dimensional (2-D) geometries and stresses out the benefit of automation of the modeling procedure. The modeling codes generated by MCPlas are used to study diffuse and filamentary DBDs in argon at subatmospheric and atmospheric pressure, respectively. The seamless transition between different levels of model complexity with respect to the considered model geometry is demonstrated. The presented investigation of a single-filament DBD interacting with a dielectric surface shows that complex phenomena of high technological relevance can be tackled using plasma models implemented in COMSOL Multiphysics via MCPlas.
LXCat is an open-access website containing data needed for low temperature plasma modeling as well as on-line tools useful for their manipulation. Display omitted
► LXCat: an open-access website with ...data for low temperature plasma modeling. ► Contains compilations of electron scattering cross sections and transport data. ► Data from different contributors for many neutral, ground-state species. ► On-line tools for browsing, plotting, up/downloading data. ► On-line Boltzmann solver for calculating electron swarm parameters.
LXCat is a dynamic, open-access, website for collecting, displaying, and downloading ELECtron SCATtering cross sections and swarm parameters (mobility, diffusion coefficient, reaction rates, etc.) required for modeling low temperature, non-equilibrium plasmas. Contributors set up individual databases, and the available databases, indicated by the contributor’s chosen title, include mainly complete sets of electron-neutral scattering cross sections, although the option for introducing partial sets of cross sections exists. A database for measured swarm parameters is also part of LXCat, and this is a growing activity. On-line tools include options for browsing, plotting, and downloading cross section data. The electron energy distribution functions (edfs) in low temperature plasmas are in general non-Maxwellian, and LXCat provides an option for execution of an on-line Boltzmann equation solver to calculate the edf in homogeneous electric fields. Thus, the user can obtain electron transport and rate coefficients (averages over the edfs) in pure gases or gas mixtures over a range of values of the reduced electric fields strength, E/N, the ratio of the electric field strength to the neutral density, using cross sections from the available databases. New contributors are welcome and anyone wishing to create a database and upload data can request a username and password. LXCat is part of a larger, community-wide effort aimed at collecting, evaluating, and sharing data relevant to modeling low temperature plasmas. To illustrate the utility of LXCat in this context, we compare electron swarm parameters in argon calculated using the different compilations of cross sections presently available on LXCat. These compilations include quite different groupings of excited states, yet lead to swarm parameters in good agreement. LXCat is available at http://www.lxcat.laplace.univ-tlse.fr.
This work presents a numerical analysis by zero-dimensional global model of the influence of electron temperature and concentration on production of OH and NO for helium plasma jet propagating in the ...atmosphere of humid air. The calculations are done for the constant electron temperatures (1–4 eV) and concentrations (10
cm
to 10
cm
). The mole fractions of air and water vapor vary from 100 to 10,000 ppm. The presented analysis reveals that at low electron temperature and H
O contents, the dissociative electron attachment to O
dominates over attachment to H
O in production of OH. At higher amount, H
O modifies the high-energy tail of electron distribution function and increases rate coefficients for electron impact processes. Dissociative electron attachment to H
O dominates in the production of OH at 1 eV and remains important at higher energies when processes with O(
D), O(
S), O
∆) produce OH. Impact dissociation of H
O dominates over the dissociative attachment at 3 and 4 eV. NO comes mainly from air effluent in the plasma and O + NO
at 100 ppm of H
O. Above 2 eV, the conversion process between OH and NO dominates in NO production at higher amount of H
O. Regarding dependencies on electron concentration, at low electron temperatures, electron distribution function is affected only at 10
cm
. But in the case of higher temperature, electron concentration and water vapor have negligible influence. The best agreement with measured data is obtained for electron concentration 10
cm
and at temperature of 2 eV for OH and 10
cm
and 3 eV for NO.
Single particle aerosol mass spectrometry (SPAMS), an analytical technique for measuring the size and composition of individual micron-scale particles, is capable of analyzing atmospheric pollutants ...and bioaerosols much more efficiently and with more detail than conventional methods which require the collection of particles onto filters for analysis in the laboratory. Despite SPAMS’ demonstrated capabilities, the primary mechanisms of ionization are not fully understood, which creates challenges in optimizing and interpreting SPAMS signals. In this paper, we present a well-stirred reactor model for the reactions involved with the laser-induced vaporization and ionization of an individual particle. The SPAMS conditions modeled in this paper include a 248 nm laser which is pulsed for 8 ns to vaporize and ionize each particle in vacuum. The ionization of 1 μm, spherical Al particles was studied by approximating them with a 0-dimensional plasma chemistry model. The primary mechanism of absorption of the 248 nm photons was pressure-broadened direct photoexcitation to Al(y2D). Atoms in this highly excited state then undergo superelastic collisions with electrons, heating the electrons and populating the lower energy excited states. We found that the primary ionization mechanism is electron impact ionization of various excited state Al atoms, especially Al(y2D). Because the gas expands rapidly into vacuum, its temperature decreases rapidly. The rate of three-body recombination (e− + e− + Al+ → Al + e−) increases at low temperature, and most of the electrons and ions produced recombine within several μs of the laser pulse. The importance of the direct photoexcitation indicates that the relative peak heights of different elements in SPAMS mass spectra may be sensitive to the available photoexcitation transitions. The effects of laser intensity, particle diameter, and expansion dynamics are also discussed.
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•Ionization mechanisms in single particle aerosol mass spectrometers are studied.•A 0-dimensional model quantifies various processes for Al particles.•Pressure broadening enables direct photoexcitation.•Electron impact ionization of excited states is the primary ionization mechanism.•Most of the electrons and ions recombine within several microseconds.
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