Growth precursors and dynamics of dust particle formation in the Ar/CH₄and Ar/C₂H₂plasmas

Abstract

This paper deals with the study of the temporal and spatial evolution of the dust formation in a capacitively coupled standard GEC cell in Ar/C 2 H 2 and Ar/CH 4 mixtures. To initiate the particle growth in the Ar/CH 4 discharge, we have either to apply transiently high power to the discharge or to inject transiently a pulse of C 2 H 2 . In the Ar/C 2 H 2 discharge, however, the particles are formed spontaneously at constant low power. The experiments underline the importance of acetylenic compounds for the nucleation process, i.e. for the first step of particle growth. Due to the different initiation process, the further temporal evolution of the dust formation is significantly different for both kinds of discharges. The dust particles are detected by means of laser beam scattering and by measuring the extinction of the laser beam after passing the discharge. The response of the plasma to the formation of dust has been analysed by emission spectroscopy and mass spectroscopy. The 7th harmonic signal of the rf driving voltage is a useful indicator for the presence of dust particles and their growth.

Dust particles in low-pressure plasmas: Formation and induced phenomena

“…3, the indication that successive generations appear is a very low frequency modulation of the signal with a typical period of about 1 min. This oscillation in electrical measurements (also observed in optical measurements) is due to the appearance of dust successive generations and has been observed by several authors in silane [16,28,46] or hydrocarbon-based plasmas [18,41]. In the case presented in Fig.…”

“…However, it is not always the case. As an example, a damping of this oscillation has been reported in acetylene, meaning that the formation or the growth are partially inhibited, or that the dust particles are removed from the plasma due to the presence of evolving detrapping forces [18,41]. On the contrary, the case presented in Fig.…”

“…Due to the previous dust particle generation, plasma conditions for dust particle formation can have changed or some inhibiting effects can have arisen. It is, for example, the case in CH 4 -based plasmas [18,27,41]. It appears that conditions for the growth of new generations of dust particles are fulfilled in dust-free spaces existing in the discharge volume.…”

“…In this last case, the fundamental requirement is the presence of molecular precursors [11]. These precursors result from the presence of reactive gases (silane SiH 4 [5,[12][13][14][15][16], methane CH 4 [17][18][19], acetylene C 2 H 2 [17,20,21]) or from material erosion (physical or chemical) at the molecular level [22][23][24][25][26]. They initiate a complex succession of chemical and physical reactions, leading to the growth of dust particles.…”

Fast nanostructured carbon microparticle synthesis by one-step high-flux plasma processing

“…3 [21][22][23][24][25][26][27][28]. Concurrently, similar nano/micro-sized carbon particles have been observed and investigated in fusion research.…”