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Behavior of high current density pulsed magnetron discharge with a graphite target

Conventional magnetron discharge with a graphite target is a technology used worldwide to deposit thin films for a large range of applications. In the last decade, the high current density sputtering regime stands out as a very interesting alternative allowing the tailoring of coating properties. The peak power density normalized to the target area can exceed 107 W m−2, leading to an important ionization of the sputtered atoms. In this paper we focused on the electrical characterization of a magnetized plasma operated at average gas pressure (5 Pa; Ar and He) with a graphite target. A cross-correlation with a high-speed gated camera and optical emission spectroscopy measurements of the plasma evolution is also given. The analysis of the plasma–surface interaction zone on the target unveiled the physical mechanisms associated with the high current density range (1.8–32.5 A cm−2), corresponding to several regimes of discharge. For graphite, it will be demonstrated that the gas rarefaction induced by the vapor wind is negligible due to its low sputtering yield. Thus, the gas recycling is the dominant mechanism sustaining the discharge, even for the higher discharge current regime when a spot is present. Spokes and other instabilities were also identified and are discussed.