Further insights into prepeak emission in pulsed radiofrequency glow discharge

详细信息    查看全文

• 作者：Rebeca Valledor^a ; Paola Vega^a ; Jorge Pisonero^a ; Thomas Nelis^b ; Nerea Bordel^a ; ^{bordel@uniovi.es}
• 关键词：Prepeak ; Temporal resolution ; Spatial resolution ; Pulsed radiofrequency glow discharge
• 刊名：Spectrochimica Acta Part B: Atomic Spectroscopy
• 出版年：2013
• 出版时间：1 July, 2013
• 年：2013
• 卷：85
• 期：Complete
• 页码：45-54
• 全文大小：569 K

文摘

Side-on optical emission measurements, with spatial and temporal resolution, have been carried out on a modified Grimm type pulsed rf glow discharge, using a copper sample and argon as discharge gas. In particular, the early ignition phase of the pulsed discharge, prepeak, and the beginning of the plateau have been electrically characterized and spectroscopically evaluated along the plasma plume for several argon and copper emission lines. Different pulse repetition frequencies have been used while keeping a constant duty cycle of 25 % , covering a range from the ¦Ìs to the ms pulsed GD. In all the cases a spatially extended discharge has been observed during the first 10-20 ¦Ìs of the pulse, when the dc bias voltage has not been fully established yet. During this early phase of the pulse, the species present in the chamber are excited following the amplitude of the voltage symmetrical oscillations, and argon and copper emission can be detected at all the distances evaluated along the plasma axis at delays as short as 4 ¦Ìs. After the first 20 ¦Ìs approximately, the discharge has contracted close to the sample surface, the dc bias voltage has been almost established and the sputtering process is taking place. Emission registered through side-on observation, at positions relatively far from the sample, decreases and then progressively increases to reach a plateau if the voltage pulse lasts long enough. Moreover, the further the detection position is from the sample surface, the later the increase of the copper and argon emission is observed. Therefore transport phenomena involving both argon and copper species are now evidently leading to an estimated average speed of 100 m/s.

Additionally, end-on optical emission measurements have been carried out to evaluate the prepeak emission from the negative glow region close to the sample surface, and then to compare this emission with that occurring at farther positions (side-on detection experiments). The results have shown that the basis of both prepeaks might be different as the prepeak signal measured using end-on detection peaks around 10 ¦Ìs later than that observed using side-on detection.