Eh Efe Kemaneci

Global (volume-averaged) model of inductively coupled chlorine plasma : influence of Cl wall recombination and external heating on continuous and pulse-modulated plasmas

An inductively coupled radio-frequency plasma in chlorine is investigated via a global (volume-averaged) model, both in continuous and square wave modulated power input modes. After the power is switched off (in a pulsed mode) an ion–ion plasma appears. In order to model this phenomenon, a novel quasi-neutrality implementation is proposed. Several distinct Cl wall recombination probability measurements exist in the literature, and their effect on the simulation data is compared. We also investigated the effect of the gas temperature that was imposed over the range 300–1500 K, not calculated self-consistently. Comparison with published experimental data from several sources for both continuous and pulsed modes shows good agreement with the simulation results.

A computational analysis of the vibrational levels of molecular oxygen in low-pressure stationary and transient radio-frequency oxygen plasma

Vibrational levels of molecular oxygen, O 2 ( v   <  42), are investigated in continuous and pulse-modulated low-pressure radio-frequency oxygen plasma with a global modelling approach. The model is benchmarked against a variety of pressure-, power- and time-resolved measurements of several inductive and asymmetric capacitive discharges available in the literature, and a good agreement is obtained. The sensitivity of the model with respect to the vibrational kinetics, the wall reactions and the spatial inhomogeneity of the charged particles are presented. The simulations without the vibrational levels are also shown for the sake of comparison.

A two-dimensional modelling study of a coaxial plasma waveguide

We present a two-dimensional (2D) plasma model for a coaxial microwave discharge. The microwave energy at driving frequency of 2.45 GHz is fed into a coaxial configuration in which the plasma acts as an outer conductor in such a way that a spatially extended surface wave is created. This geometry permits large surface treatment, especially if a set of such coaxial lines are used. The 2D model describes the plasma as a two-temperature non-chemical equilibrium fluid sustained by electromagnetic surface waves. We present results for argon as a working gas. The importance of wave–plasma power coupling and electron heat transport is discussed. The radial localization of electron density in the coaxial plasma waveguide is observed and compared with experimental results. Moreover, a parameter study allows one to investigate the dependence of radial contraction of the electron density as a function of pressure in the range 2–8 mbar, and also the dependence of electron density with power input in the range 120–1200 W. In order to verify the model, the modelling results are compared with experimental results for the electron density and temperature and good agreement is found.

Modelling of an intermediate pressure microwave oxygen discharge reactor: from stationary two-dimensional to time-dependent global (volume-averaged) plasma models

A microwave-induced oxygen plasma is simulated using both stationary and time-resolved modelling strategies. The stationary model is spatially resolved and it is self-consistently coupled to the microwaves (Jimenez-Diaz et al 2012 J. Phys. D: Appl. Phys . 45 335204), whereas the time-resolved description is based on a global (volume-averaged) model (Kemaneci et al 2014 Plasma Sources Sci. Technol. 23 045002). We observe agreement of the global model data with several published measurements of microwave-induced oxygen plasmas in both continuous and modulated power inputs. Properties of the microwave plasma reactor are investigated and corresponding simulation data based on two distinct models shows agreement on the common parameters. The role of the square wave modulated power input is also investigated within the time-resolved description.

A global model of cylindrical and coaxial surface-wave discharges

A volume-averaged global model is developed to investigate surface-wave discharges inside either cylindrical or coaxial structures. The neutral and ion wall flux is self-consistently estimated based on a simplified analytical description both for electropositive and electronegative plasmas. The simulation results are compared with experimental data from various discharge setups of either argon or oxygen, measured or obtained from literature, for a continuous and a pulse-modulated power input. A good agreement is observed between the simulations and the measurements. The calculations show that the wall flux often substantially contributes to the net loss rates of the individual species.

Global modelling of cylindrical surface-wave discharges: Argon or oxygen

Summary form only given. Surface wave-discharges are often used for a variety of technological purposes mostly due to their stability and efficacy for a wide range of operation parameters. They are associated with a large ratio of axial to radial dimension compared to other types of plasma sources and this allows them to cover relatively larger areas. In order to probe the underlying physical principals, a variety of detailed modeling approaches are already developed, however, much less attention is paid on computationally efficient global models. In this contribution, a self-consistent global modeling approach is developed and implemented on a variety of cylindrical surface-wave discharges operated in oxygen or argon. The simulation results are compared with a variety of measurements on surfatron and coaxial plasma-line and an agreement is obtained.

Simplifying plasma chemistry via ILDM

A plasma fluid model containing a large number of chemical species and reactions yields a high computational load. One of the methods to overcome this difficulty is to apply Chemical Reduction Techniques as used in combustion engineering. The chemical reduction technique that we study here is ILDM (Intrinsic Lower Dimensional Manifold). The ILDM method is used to simplify an argon plasma model and then a comparison is made with a CRM (Collisional Radiative Model).

Global model of inductively coupled radio-frequency Cl 2 plasma: Dissociation, excitation and power modulation

Summary form only given. Plasmas are commonly used for industrial surface processing. Reactive molecular gases are used which have complex chemical kinetics. For example, Cl2 is widely used for plasma etching processes. The electronegative nature of this molecular gas makes the investigation harder, compared to electropositive atomic plasmas. Dissociation of Cl2 by electronic collisions is substantial, in addition to the ionization processes. Negative and molecular positive ions are produced. Additionally, atomic and molecular excited levels play an active role. We have modelled an inductively coupled radio-frequency Cl2 plasma via a global model. The plasma is formed in a cylindrical column with a pressure range of 2-50 mTorr and power input 100-500 W, and includes gas-phase and surface reactions. Although a steady state global model of Cl2 has been presented, a detailed study of excited state atoms and molecules, as well as the effect of power modulation has not been made. Compared to Thorsteinsson et. al., we have added spin-orbit excited Cl(P1/2) and use an updated set of rate coefficients for electronic and vibrationally excited Cl2. The steady-state particle densities and electron temperature are calculated as a function of power input and the pressure, and compared to experimental results, giving reasonable agreement. In the future we plan to extend the model to time-resolved densities in pulse-modulated plasmas.