Oscillating electric fields in the megahertz range have been studied in a high power impulse magnetron sputtering (HIPIMS) plasma with the use of electric field probe arrays. One possible reason for these oscillations to occur is due to charge perturbation -or so called modified two-stream instabilities (MTSI). It is known that MTSI give rise to acceleration of the charged plasma species, and can give a net transport of electrons across the magnetic field lines. Measurements of these oscillations confirm trends, specifically of the frequency dependence on ion mass and magnetic field strength as expected from the theory of MTSI waves. These results help to explain the previously reported anomalous fast electron transport in HIPIMS discharges, where classical theory of diffusion, using collisions to transport electrons has failed.

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Recent developments in plasma assisted physical vapour deposition (PAPVD) processes are reviewed. A short section on milestones in advances in PAPVD covering the time period from 1938 when the first PAPVD system was patented to the end of the 1980s is followed by a more detailed discussion of some more recent advances, most of which have been related to increases in plasma density. It has been demonstrated that the state of the art PAPVD processes operate in a plasma density range of 1011 to 1013 cm-3. In this range a substantial fraction of the plasma consists of ionized film forming species. Hence, the energy of the condensing film forming species can be directly controlled, as opposed to utilizing indirect energy control with, for example, ionized inert gas bombardment. For a large variety of applications ranging from ceramic film synthesis at conditions far from thermodynamic equilibrium to state of the art metallization technology, such direct energy control of the condensing film forming species is of critical importance, and offers the possibility to engineer the coating microstructure and hence the coating properties.

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Polycrystalline TiN/NbN superlattice coatings were deposited on M2 tool steel substrates using an opposed dual-cathode unbalanced magnetron sputtering system. Superlattice deposition was achieved by placing the substrates on a cylindrical holder that rotated on an axis equidistant between, and parallel to, the faces of opposed Ti and Nb targets. Cross contamination of the targets and the alternating superlattice layers was minimized using a baffle or an extra-large cylindrical substrate holder. The superlattice period was determined by the substrate holder rotation speed. Analytical techniques including x-ray diffraction, energy-dispersive spectroscopy and transmission electron microscopy were used to characterize the structure of the supedattice coatings. Microhardness values for the superlattice coatings as high as 5200 kg/mm 2 HVO.05 have been achieved, comparable to the reported highest hardness values of single crystal TiN/VN, TiN/V o . 6 Nb oA N and TiN/NbN superlattice coatings. The results indicate that the hardness of the polycrystalline TiN/NbN supedattice coatings is affected not only by superlattice period, but also by nitrogen partial pressure and ion bombardment during deposition.