Publication details

Rotating spokes in reactive HiPIMS process measured by spatially resolved OES



Year of publication 2022
Type Conference abstract
MU Faculty or unit

Faculty of Science

Description The rotating plasma patterns, also known as spokes, spontaneously appearing in E × B magnetised plasma discharges, such as Hall thruster and high power impulse magnetron sputtering (HiPIMS) discharge, have been thoroughly investigated mainly in the non-reactive atmosphere under many different experimental parameters. Among other things, it has been discovered that the presence of spokes enhanced the transport of sputtered species from the target to the substrate, leading to a much more energy efficient HiPIMS process. Due to the reactive processes being widely used in industry, there is an effort to find out more information about spokes in reactive atmospheres and their effect on the deposition process and the transport of sputtered species at those conditions. The use of spatially resolved optical emission spectroscopy in a single-shot mode is one of the possibilities for a deeper understanding of the spokes. In this contribution, the non-invasive spatial-resolved OES of the spoke was conducted in reactive HiPIMS discharge. The HiPIMS pulses were 100 µs long with a repetition rate of 5 Hz. The 3-inch titanium target, argon as working gas, and nitrogen as reactive gas were utilised. The constant total pressure was set to 1.0 Pa. Different reactive gas flows were applied to measure the properties of spokes in both metallic and poisoned modes. The fast photodiode and the Langmuir probe were used to capture and determine the position of the passing spoke. The signals from the photodiode and the Langmuir probe were synchronised with the spectrometer and an ICCD camera. The ICCD camera possesses a dual-image-feature mode, which allows capturing two consecutive images with only a 1.5 µs delay between them. It enabled us to determine the spoke propagation velocity. The single-shot measurements ensured that one waveform and one double image were acquired simultaneously from a single HiPIMS pulse for each spectrum. The spatial-resolved emissions of argon, nitrogen, and titanium atoms and ions spectral lines were investigated within the spoke passing by the probes.
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