Erlangen 2018 – wissenschaftliches Programm

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P: Fachverband Plasmaphysik

P 2: Low Pressure Plasmas I

P 2.2: Vortrag

Montag, 5. März 2018, 11:00–11:15, KI 1.174

Probing the Electron Density of Spokes in a HiPIMS Plasma Using Target Inserts — Ante Hecimovic, •Julian Held, Volker Schulz-von der Gathen, Wolfgang Breilmann, Christian Maszl, and Achim von Keudell — Experimental Physics II, Ruhr-University Bochum, Germany

In High power impulse magnetron sputtering (HiPIMS) a magnetron discharge is operated with short, high-voltage pulses, creating a highly dense plasma. Those pulses have a length in the order of 100 µs and power densities of several kW cm⁻². At high discharge currents, the plasma emission is not homogeneous but is instead organized into distinct zones of high plasma emission, which rotate in ExB direction a few mm above the target surface. These so called "spokes" are thought to improve ion transport to the substrate and might therefore be the key to improve the deposition rate. The strong emission indicates an elevated electron density. However, it would disturb the plasma considerably to position a probe in the vicinity of the target. Therefor, no direct measurement of the electron density inside the spokes has been performed. In this contribution, small electrically isolated inserts in the target surface were used to probe the local current density. Simple sheath theory was then applied to derive the electron density at the sheath edge. The electron density was in the order of 10¹⁹ m⁻³ and scaled linearly with discharge current. The electron density was elevated by about 50% when a spoke was present above the insert.