(As discussed in Section 3.1., all discharges take place in HPPMS mode and reach a peak power density close to or even inside the HiPIMS mode defined by Gudmundsson et al.
As a result of the discharges mode, face-centred cubic AlTiN grains with strong 200-reflection intensities were detected, which are typical for AlTiN HPPMS coatings as referred by other authors [15, 35].
So, AlTiN coatings deposited by HPPMS generally show a denser and smoother structure without column growth than coatings deposited by dcMS at the same average power due to increased metal ion bombardment .
In addition, they are beneficial to compare the coating properties achieved through HPPMS with the ones of other PVD technologies, such as dcMS or cathodic-arc evaporation.
In particular, other studies show that the high number of metal ions with high energies in HPPMS discharges support the formation of fcc-AlTiN (200) phases with higher hardness than the one of the dcMS typical fcc-AlTiN (111) phase .
Analyses on surface morphology and topography of AlTiN coatings depending on HPPMS pulse-frequencies were performed by atomic force microscopy (AFM).
However, AlTiN coatings deposited with HPPMS generally show a smoother surface than AlTiN coatings deposited by dcMS.
In summary, the study shows that the surface roughness of AlTiN coatings sputtered by HPPMS is strongly affected by the pulse-frequencies and the resulting discharge parameters, especially current density and power density.
In this study, the influence of the HPPMS frequency on plasma discharges and AlTiN coating properties was investigated with focus on the relation between the plasma and deposition conditions.
The results also demonstrate the advantages of AlTiN coatings deposited by HPPMS comparing to coating deposition by dcMS:
(1) AlTiN coatings by HPPMS show smoother surfaces as AlTiN coatings by dcMS.
(3) HPPMS improves the coverage and uniform coating thickness of complex-shaped substrates because the increased number of ions together with the bias potential allows controlling the layer-forming particles.