The influence of the respective durations of the discharge and the afterglow on the reactivity of a DC pulsed plasma used for iron nitriding

Abstract

The optical diagnostics of a DC pulsed plasma used for iron nitriding is carried out for various plasma conditions. The fluorescence of the first negative and the second positive systems of is observed in the time afterglow, in order to obtain some insights into the creation and the loss processes of and states. An iron emission line is also observed which is indicative of the sample sputtering. Particular attention is paid to the influence of the gas pressure on the respective durations of the discharge and the afterglow. Analysis of the plasma both during the discharge and during the post-discharge leads to the determination of favourable conditions for the surface treatment. It is also shown that the electron density in the discharge can be deduced from the line intensity decay in the afterglow.

Experimental investigation of the electrical characteristics and initiation dynamics of pulsed high-voltage glow discharge

“…In fact, it very much depends on the density of the primary plasma just before each discharge pulse. As previously reported, [24,25] the electron density is proportional to the discharge current, and the decay of the N + 2 density after the glow discharge can be described by [25] I t = I t=0 (1 + αn e0 t) 2 (3)…”

“…The electron density thus decreases potentially with time. For a pressure condition of several Torr, the decay of the electrons requires a duration of several milliseconds [25]. Therefore, it is recommended that the post-discharge time during pulsed glow discharge must not exceed several milliseconds in order to limit the cooling of the neutral gas and to facilitate the discharge after the plasma has been turned off.…”

Deposition of carbon based materials by continuous and pulsed discharges

“…the time between two successive pulses, and the duty cycle [DC5(t ON / t P )6100]), indicating the percentage of the period in which the discharge is ON. The investigation of these two modulation parameters has been widely documented in the literature by considering various types of discharges (dc, rf and mw) [7][8][9] and different gases employed in material processing, 4,8,[10][11][12][13][14] as well as from theoretical and experimental points of view. 9,15 Generally, the beneficial effects of modulation are observed when the pulse period is shorter than the species residence time in the reactor as well as the lifetime of the reactive species; on the contrary, at pulse periods larger than the residence time and lifetime, the system reaches a state similar to the CW conditions, and the modulation becomes ineffective.…”

“…the time between two successive pulses, and the duty cycle [DC = ( t ON / t P )×100]), indicating the percentage of the period in which the discharge is ON. The investigation of these two modulation parameters has been widely documented in the literature by considering various types of discharges (dc, rf and mw)7 – 9 and different gases employed in material processing,4,8,10 – 14 as well as from theoretical and experimental points of view 9 9,15…”

Study of polycrystalline diamond deposition by continuous and pulsed discharges

“…the time between two successive pulses, and the duty cycle (DC = T ON T PERIOD ⋅100), indicating the percentage of the period in which the discharge is ON. The investigation of these two modulation parameters has been widely documented in literature by considering various types of discharges (dc, rf and mw) [1][2][3] and different gases employed in material processing, (i.e. material treatment [4], thin film etching [5] and deposition [2,6]) from theoretical and experimental points of view [3,7,8].…”