Plasma properties as function of time in Ar/C₂H₂ dust-forming plasma

Abstract

The time-dependent properties of an Ar/C2H2 dusty plasma (neutral, ion and electron densities, effective electron temperature and dust charge) are studied using a volume-averaged model for conditions corresponding to experiments on nanoparticle growth. The calculated density evolution for C2H2, H2 and C4H2 molecules are compared with time-resolved measurement of the mass peaks of the neutral species and the effects of the dust density on the plasma properties are analyzed. Time evolutions of the main positive and negative ions are also obtained thanks to the calculations. As a consistency check the time-dependence of the dust radius is also obtained numerically, assuming that an increase of the dust radius is due to deposition of hydrocarbon ions and C2H radicals on the surface of dust particles. It is shown that for conditions corresponding to the experiment, the ions are the main contributor to the particle growth. The calculated dust growth rate is compared to the time-dependence of the dust particle size obtained in the experimental measurements. The results of the numerical calculations are found to be in a good qualitative agreement with the experimental data.

Effects of Argon Atoms in Excited States on Properties of Argon-Acetylene Dusty Plasma

“…The input fluxes of acetylene and argon are taken to be 1.5 sccm and 11.0 sccm, respectively, as in the experiment of our interest [7 -9]. It is assumed that the energy distribution for ions is Maxwellian, and that the ions and dust particles are at gas temperature T g (300 K), while the electron energy distribution function (EEDF) F is assumed to be Druyvesteyn-like [7,9]. The EEDF has the follow- (2 / 3 ) ( )…”

“…The model accounts for various processes of the loss and generation of the discharge species, including the processes on dust particles and plasma walls, the collisional processes in the bulk plasma, as well as the pumping of gas in and out of the chamber. The processes and their rates are described in [7,9]. The effective electron temperature is found from the power balance equation…”

“…where P abs = 9 W is the absorbed power as in [7], V is the volume of the discharge chamber, the power loss P loss = P coll + P w + P d , where P coll is the power loss due to elastic and inelastic electron-neutral collisions [7,9], P w and P d are the power losses due to charged particle fluxes to the walls and to the dust particles, respectively [7,9]. The dust charge Z d is found, assuming that the charging of dust particles is due to electron and ion fluxes onto their surfaces, taking into account for the non-Maxwellian shape of the EEDF and collisions of ions with neutrals in the sheaths around dust particles [7,9].…”

“…Since the threshold energy for ionization of C 2 H 2 is larger than that for dissociation of acetylene molecules, it is assumed here that the rate for dissociation of C 2 H 2 in collisions with Ar* atoms is nearly 2 times larger than the ionization rate. More information on the rates for various generation and loss processes, considered in our model, can be found in [7,9].…”

“…Reactive plasmas with growing inside of plasma volume nano-and micro-sized particles (dust particles) are of a great fundamental interest and are also useful for various technological applications [1]. Carbonaceous dust particles are usually formed in gas mixtures containing methane, acetylene or ethylene and, therefore, gas discharges in these gas mixtures have been investigated in many works [2][3][4][5][6][7][8][9].…”