Direct observation of spoke evolution in magnetron sputtering

• Published in: Applied physics letters Vol. 111; no. 6
• Main Authors: Anders, André, Yang, Yuchen
• Format: Journal Article
• Language: English
• Published: Melville American Institute of Physics 07-08-2017
• Subjects: Applied physics; Direct current; Evolution; Ionization; Magnetron sputtering; Photovoltaic cells; Spokes; Streak cameras; Substructures
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.4994192

Ionization zones, also known as spokes, are plasma instabilities manifested as locations of intensified excitation and ionization over a sputtering magnetron's racetrack. Using a linear magnetron and a streak camera, we were able to observe and quantify spoke dynamics. The technique allows us to image the onset and changes for both direct current magnetron sputtering (dcMS) and high power impulse magnetron sputtering (HiPIMS). Spokes in dcMS exhibit substructures. Spokes in HiPIMS are not stable as they shift along the racetrack; rather, they tend to grow or diminish, and they may split and merge. Their evolution can be interpreted in the context of localized electric fields and associated electron heating.