Publication details

Evolution of ionization fraction of sputtered species in standard, multi-pulse and reactive HiPIMS

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Year of publication 2020
Type Conference abstract
MU Faculty or unit

Faculty of Science

Description High power impulse magnetron sputtering (HiPIMS) attracts the interest of the industry as the coatings deposited by HiPIMS exhibit enhanced properties compared to dc magnetron sputtered (dcMS) coatings. This is caused by very dense plasma generated in HiPIMS, which results in a large fraction of ionized sputtered particles. However, a significant drawback of HiPIMS is a lower deposition rate compared to dcMS, which can be mitigated by the operation of HiPIMS in multi-pulse mode (m-HiPIMS). M-HiPIMS further changes the coating structure and resulting properties due to the enhanced ion flux to the substrate. An effective branching fraction method is utilized to study the evolution of the sputtered species ionization fraction derived from the absolute ground state number densities of the sputtered titanium species. Influence of the preceding pulse on the subsequent pulse is examined as a function of delay between them. In reactive HiPIMS, the hysteresis curve is generally reduced in width and shifted towards lower reactive gas supplies compared to reactive dcMS. We report on the evolutions of the sputtered species ionization fraction in reactive HiPIMS with oxygen, nitrogen and acetylene gases. The sputtered species ionization fraction increases with the partial pressure of the reactive gas, which is attributed to a combination of different effects taking place in HiPIMS plasma. Further, the hysteresis curve shape changes with the change of the repetition frequency. Larger ionization fraction of the sputtered species leads to a larger difference in the hysteresis curve shape. The hysteresis behavior is modelled utilizing a modified Berg model, where the back-attraction of the sputtered species to the target is incorporated. The results from simulations prove that the back-attraction of sputtered metal ions is the main effect causing the hysteresis curve reduction and shift in reactive HiPIMS.
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