Investigation of ionized metal flux fraction in HiPIMS discharges with Ti and Ni targets

• Ionized metal flux fraction in HiPIMS of Ni and Ti determined in Ar and Ar + O2 atmosphere
• Substantial increase in the ionized fraction observed in reactive mode
• Gridless analyzer developed, suitable for low deposition rate processes

Ionized metal flux fractions in high power impulse magnetron sputtering (HiPIMS) were analyzed by a combination of a retarding field analyzer and a quartz crystal microbalance (QCM). Two target materials, Ni and Ti, were studied in an Ar atmosphere. In the case of Ti, the reactive (Ar + O2) mode was also investigated. Ionized metal flux fractions of up to 50% for Ni were observed at a pulse power density of 1 kW cm− 2. The pulse on-time had negligible influence on the ionized fraction. Somewhat higher values, exceeding 60%, were measured for Ti at 2 kW cm− 2. In this case, shorter on-times led to higher ionized fractions at the same deposition rate and average discharge power density. In reactive sputtering of Ti, substantially higher ionized fraction was observed in the oxide mode as compared to the metal mode. Already at lower values of the pulse power, there was a significant fraction of Ti ions in the flux.