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L. Zauner, T. Wojcik, T Kozák, J Capek, H. Bolvardi, S. Kolozsvári, P.H. Mayrhofer, H. Riedl:
"Integral and Time-Resolved Ion Distribution Functions in a Reactive Ti-Al HiPIMS Discharge";
Poster: 47th International Conference on Metallurgical Coatings and Thin Films, ICMCTF, San Diego, CA, USA; 2021-04-26 - 2021-04-30.

Within the everlasting scientific topic of pushing the boundaries for Al solubility limits (xmax) in Ti-Al-N based coatings, reactive high-power impulse magnetron sputtering (R-HiPIMS) has been established as one key-technology. The introduction of enhanced ionization rates allows for additional pathways in tuning the structural and chemical evolution by surface-diffusion driven growth. Hence, especially depending upon the charge state and mass-ratio of the metal-ions incident on the growing film, metastable thin films are decisively influenced in their overall growth characteristics.
Here, we review in detail the dependence of the phase-stability, and hence xmax, on varying deposition parameters during R-HiPIMS of Ti-Al-N thin films using Ti1-xAlx composite targets (x = 0.40, 0.50 and 0.60). The influence of HiPIMS pulse parameters such as frequency, pulse length, or peak power density, but also of deposition parameters including N2 partial pressure, substrate bias voltage, or target compositions were investigated methodically. The so obtained coating structures were analysed with respect to phase-stability, thermomechanical properties, and morphology applying nanoindentation, X-ray diffraction combined with electron imaging techniques. The systematic studies revealed an Al solubility limit of xmax~0.55, obtained for a duty cycle of 3.75 % (peak power density of ~1 kW/cm2) and a N2-to-Ar flow-rate ratio of 0.3. Moreover, sufficient intermixing of the arriving film species controlled via bias potentials (DC as well as discharge synchronised) was observed as decisive for the deposition of high Al containing fcc-structured coatings. To gain a further insight in the growth kinetics of selected coatings, time- and energy resolved mass-spectroscopy measurements have been conducted. Based on these analyses, the ratio and energy of simultaneously arriving Tin+- and Aln+-ions at the substrate surface, are highly influential for stabilising the preferred cubic modification with respect to the prevailing deposition conditions.

R-HiPIMS; Ti-Al-N; Phase Formation; Deposition Parameters; Mass-spectroscopy;

Project Head Helmut Riedl:
CDL-SEC