Publication details

Single-Shot Spatially Resolved Optical Emission Spectroscopy of Plasma Species within the Spoke

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Year of publication 2021
Type Conference abstract
MU Faculty or unit

Faculty of Science

Description Using the fast cameras it has been revealed, that the plasma above the race track rearrang-es under certain conditions into localised ro-tating regions of increased light emission and intense excitation, commonly known as spokes or ionization zones. Over time, the spokes have been observed in many types of magnetron sputtering discharges, including the reactive processes. The spokes have been studied due to their potential impact on the sputtering process and, consequently, thin film deposition. It has been discovered, that spoke’s parameters, such as the mode num-ber, shape and speed of rotation, are depend-ent on practically all experimental conditions, including the magnetic field and target mate-rial in combination with working gas. This contribution presents the single-shot spa-tially resolved optical emission spectroscopy (OES) of the titanium and argon species pre-sent within the spoke captured by the Lang-muir probe and the optical fibre both placed in the deposition chamber in a non-reactive high power impulse magnetron sputtering (HiPIMS) discharge (Figure 1). The argon gas pressure in the range of 0.4 – 1.6 Pa has been set to investigate both triangular (< 0.5 Pa) and round (> 1.0 Pa) spokes. The Langmuir probe recorded the floating potential of the passing spoke in each HiPIMS pulse, there-fore the time-resolved measurement could be utilized to spatially resolve the passing spoke. It was always possible to distinguish at least two spokes on the electrical and the optical signals, therefore, determining where one spoke begins and where it ends. By pro-cessing those signals, we were able to calcu-late a spoke length distribution, and conse-quently, by creating a normalised time scale of each spoke, the unified spoke has been created. To reveal additional spoke’s inner parameters the spatially resolved excitation temperature and the ionisation fraction were obtained from the emission signal.
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