Uniform propagation of cathode-directed surface ionization waves at atmospheric pressure

Abstract

The uniform propagation of positive-polarity surface plasmas in air at atmospheric pressure has been achieved using a multi-layer structure, consisting of a silicon wafer covered by a 1 µm thick dielectric SiO2 layer as a propagation surface. Instead of the branched streamers observed in the same conditions when using conventional bulk dielectric surfaces, the plasma exhibits a homogenous ring-shaped structure with a high degree of reproducibility and stability. The plasma is generated by applying nanosecond positive voltage pulses to a tungsten wire touching the dielectric surface. The plasma has been imaged in single shot operation at high spatial resolution with an ultraviolet reflective microscope coupled with a fast intensified charge-coupled device camera. Time-and space-resolved optical emission spectroscopy shows that the homogenous ring corresponds to the propagation of an ionization front with a region of high N2 + * emission. We discuss the origin of the ring-shaped ionization wave, considering the role of the Si-SiO2 interface and the effect of illumination by an external light source. The ring ionization wave may result from branching inhibition, due to a photoelectric effect at the interface created by the photons emitted by the plasma. The generation of stable uniform surface ionization waves, in ambient air at atmospheric pressure, could be of interest for further advanced plasma-surface interaction studies or flow control applications.

Remote streamer initiation on dielectric surface

“…positive/negative streamer, negative-ion drift, fast ionisation waves under nanosecond voltage pulses etc. [1,2,7,[9][10][11][12]. This fact is especially important for electronegative gases at highpressure, like for example air, where these mechanisms may result in complex filamentary appearance of the discharge.…”

Complicated streamer dynamics in petal‐like patterns formed on the substrate downstream of an argon plasma jet

“…What's more, the sepals and the petals are interleaved. Since the dynamic behaviors of the star-shaped discharge (D p1 ) and the disk-like one (D n ) have been investigated in the literature, [34,37] much attention will be paid to the spatiotemporal evolution of the fork-like petals (D p2 ) in the following.…”

“…In most cases, surface streamers are distributed uniformly along radial directions, and a homogeneous disk is observed on the substrate. [32][33][34] Sometimes, they propagate anisotropically, leading to the formation of a star-shaped pattern. [35][36][37] For the anisotropic surface streamers, after propagating a certain distance, they may split and then propagate along a circular arc.…”

Experimental and 2D fluid simulation of a streamer discharge in air over a water surface

“…However, the propagation at/over the surface is less understood due to the presence of a complex air-plasmamedium interface characterized by discontinuities of several parameters, such as density, chemical composition, dielectric permittivity, electrical conductivity, and others. Studies reporting such discharges, also known as surface discharges [7], are numerous [8][9][10]. However, those addressing the transition from propagation in the gap to the surface are scarcer.…”

“…Xiong and Kushner [21] have highlighted that such a ring-to-dot transition is probably due to the destabilization of the ring by random photoionization events. Moreover, Darny et al [9] investigated the influence of the surface properties on the emission behavior by discharging over SiO 2 -Si and glass plates. In the first case, the emission consisted of a homogeneous ring, while in the second case the emission consisted of filaments.…”