The study of the physical processes of low-temperature plasma formation and its effects on metal product surface

Abstract

Abstract. The article examines the physical processes associated with the formation and the impact of low-temperature plasma of combined discharge on the surface of metal products. It has been shown theoretically and experimentally that the propertiesgas discharge and the results of its action on the product surface depend significantly on the sign of the bias potential.

Study of the properties of the asymmetric microwave low pressure gas discharge

“…In [17][18][19], it was shown that near the workpiece surface (figures 1(b) and 3) a plasma layer adjacent to it is formed, having a width of the order of the ampl itude of spatial electron oscillations x 0 , which turns out to be depleted of electrons due to their falling on the workpiece. As a result, part of the ion plasma core is exposed in this area, and an oscillating near-surface layer of a positive space charge is formed.…”

“…Due to the small amplitude x 0 of plasma electron oscillations in the microwave field and, consequently, the small thickness of the arising surface layer d ≈ x 0 ∝ ω −2 with ϕ 0 = 0 the value U p ≈ 10-20 V [17,18], which is significantly less than the one characteristic of the high frequency discharge [19] where it reaches hundreds of volts.…”

“…With ϕ 0 ⩽ 0 near the surface, as was shown in [17,18], a near-surface layer of positive space charge is formed which determines the value of the positive stationary (average over the field period) potential U p of the quasi-neutral plasma in regard to the sample. Ion bombardment of the product occurs and the surface of the resonator chamber.…”

“…One of the main areas of research in this regard is the research into the effect of high-frequency (ω ~ 2π • 10 6 -2π • 10 8 s −1 ) (HF) low-pressure gas discharge on the product surface, which was studied experimentally [4][5][6] and theoretically [7][8][9][10][11][12][13][14]. Earlier, in [15][16][17][18][19], the effect of a low-pressure combined gas discharge on the metal surface was examined. The low-temperature plasma generated in the original (developed by the authors) processing plant is formed near the product surface under the influence of two factors: microwave (1.54 • 10 10 s −1 ) electromagnetic field generated by the magnetron in the resonator chamber, and the electrostatic field that occurs when a static bias potential is applied to the product ϕ 0 ≈ 50-250 V. In this case, the input microwave power is only 30-150 W, which is significantly lower than the power of the units P 0 ~ 200-500 W used to process products with HF discharge plasma [19].…”

“…Ion bombardment of the product occurs and the surface of the resonator chamber. Note that when ϕ 0 = 0 and frequency of the microwave field 1.54 • 10 10 s −1 the value of the stationary potential is only U p ≈ 10-20 V [17,18]. The near-electrode layer borders on a layer of a quasineutral microwave plasma characterized by an ambipolar diffusion mode [19].…”