An experimental and theoretical investigation of a magnetically confined dc plasma discharge

Abstract

A magnetically confined dc plasma discharge sustained by a thermionic source was investigated using a combined experimental and theoretical approach. The discharge originates in an arc plasma source and is expanded in a cylindrical chamber, where it is stabilized by an annular anode. The plasma expansion is contained by an axial magnetic field generated by coils positioned at the top and the bottom of the reactor. The plasma reactor design allows control of the energy of ions impinging on the substrate and thus a high electron density of about 1017 m−3 at 1 Pa can be reached. The plasma is studied using a model composed of the Poisson and of the charged species continuity equations, solved in the flow and temperature fields determined by solving the Navier–Stokes and Fourier equations. The model equations are integrated using the finite element method in a two-dimensional axial symmetric domain. Ionization rates are either assumed constant or determined by solving the Boltzmann transport equation in the local electric field with the Monte Carlo ͑MC͒ method. Electron and ion transport parameters are determined by accounting for magnetic confinement through a simplified solution of the ion and electron momentum conservation equations, which yielded parameters in good agreement with those determined with the MC simulations. Calculated electron densities and plasma potentials were satisfactorily compared to those measured using a Langmuir probe. The model demonstrates that the intensity of the magnetic field greatly influences the electron density, so that a decrease by a factor of 2 in its intensity corresponds to a decrease by almost an order of magnitude of the electron and ion concentrations

Langmuir probe plasma parameters and kinetic rates in a Ar–SiH4–H2plasma during nc-Si films deposition for photovoltaic applications

“…The rate constant k gas for the gas-phase reaction of silane to atomic hydrogen (table 2, reaction (j)) has been estimated from temperature dependent fit functions available from experimental evaluations (table 3). The gas temperature at the two regions (r = 0-4 cm and r = 6-8 cm) of 500 K and, respectively, 400 K was obtained from a multi-scale fluid model of the LEPECVD [34].…”

Challenges of introducing quantitative elementary reactions in multiscale models of thin film deposition

“…The investigated plasma reactor is a low‐energy plasma‐enhanced chemical vapor deposition (LE‐PECVD) apparatus that can be used to deposit high quality Si films at high growth rates using SiH 4 as gas phase Si precursor 106–108. Briefly, the plasma reactor is structured as follows.…”

“…The reactor macroscale model adopted to study the plasma chemistry consists of two parts, a first focused on the electromagnetic properties of the plasma discharge (the discharge model) 106 and a second on the description of the gas phase and surface chemistry (the chemistry model) 109. In the macroscale model the reacting surface appears as a boundary condition in the mass conservation equations of gas phase species, while the surface chemical composition is determined locally by solving the pseudo steady state mass conservation reaction for the adsorbed species.…”

Investigation of magnetic field and shielding gas in electro-discharge deposition process

“…It is stated in the research works 16–18 that magnetic field when used in plasma discharge process, the plasma particles in the plasma channel are influenced by electromagnetic field and Lorentz force. Literature 19–21 shows that the application of magnetic field is used in the welding research areas, to increase the quality of welding by confining the plasma discharge. From the EDAX compositional analysis of Muralidharan and Chelladurai 15 along with the tool material deposited, the inclusions of carbon and oxygen are also observed over the workpiece in the EDD process with air as the dielectric medium.…”