Studies of glow discharge oscillations and jet-enhanced cathodic sputtering

• Main Author: Zhu, Zhubiao
• Other Authors: Piepmeier, Edward H.
• Language: en_US
• Published: 2012
• Subjects: Glow discharges; Sputtering (Physics)
• Online Access: http://hdl.handle.net/1957/34651

Three aspects of glow discharges have been studied: glow discharge oscillations, sputtering, and coupling between cathode and anode regions the two most important regions in a glow discharge. Cathode and anode processes are tightly coupled by electron and ion coupling effects. Both electron and ion coupling effects were observed by studying excited Ar atoms in the cathode and anode regions and observing laser-induced space charge variations and the optogalvanic effect. Laser-induced space charge variations in the glow discharge were observed by the change in potential of an electrical probe. This signal, called the optopotential signal, provides useful information about the cathode and anode processes, and may become another useful spectroscopic detection method. Glow discharge oscillations are old phenomena but our mechanistic understanding of the processes involved continues to grow. A mechanism study is important especially now since a new type of sensitive GC detector is being developed based on this phenomenon. A SPAN model of glow discharge oscillation is proposed: source formation, propagation, accumulation, and neutralization of space charges. Electrode coupling couples the neutralization and source formation processes thus completing the feedback loop necessary for some of the observed oscillations to occur. Four modes of oscillations were found. Emission, space potential and current monitoring, and forced oscillations were used to monitor and identify the mechanisms. Studies of cathodic sputtering with gas flow rates up to 2.13 L/min/jet were carried out in an Atomsource sputtering atomizer with Ar as the jet gas and Cu as the cathode sample. These flow rates are 20-fold greater than those normally used and were found to increase net sputtering yield significantly. A fourfold increase in net sputtering yield was observed when the number of jets in use was decreased from six to one, with the gas flow rate and other conditions held constant. Possible explanations for these effects are offered. === Graduation date: 1996