Influence of bipolar pulsed DC magnetron sputtering on elemental composition and micro-structure of Ti–Al–Y–N thin films

Single-phase cubic Ti1 − xAlxN thin films with high Al content are preferred in industrial applications as they combine superior mechanical properties with good oxidation protection. ly we showed that yttrium, which can further increase the oxidation resistance by the reactive element effect, shifts the cubic stability range of Ti1 − xAlxN to lower AlN mole fractions. Already the addition of 1 at.% Y to single-phase cubic Ti0.45Al0.55N promotes the hexagonal phase formation. on X-ray diffraction and transmission electron microscopy studies we reveal that DC magnetron sputtering (DC-MS) from Ti0.49Al0.49Y0.02 compound targets in Ar–N2 atmosphere results in the formation of mixed cubic-hexagonal structured (Ti1 − xAlx)1 − yYyN films, whereas the cubic structure can be stabilized by employing bipolar pulsed magnetron sputtering. This can be correlated to an increase in the Ti/Al ratio of the film and increased ion bombardment with increasing pulse duration, triggered by increases in the plasma electron temperature and ion fluxes. For pulsed DC-MS with 80 kHz and increasing pulse duration from 0 (DC-MS) to 4976 ns the composition of the coatings changes from Ti0.41Al0.57Y0.02N to Ti0.46Al0.52Y0.02N and the structure from a mixed cubic-hexagonal to a single-phase cubic, resulting in hardness increases from 23.5 to 34.6 GPa, respectively.