Dual Source Pulsed Plasmas for the Production of Ultra-High Performance Coatings

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Pulsed processing has initiated a new era in surface engineering technologies. For example, pulsed magnetron sputtering has transformed the deposition of dielectric materials. The benefits of pulsed processing can be further capitalised on through the application of mid-frequency pulsed DC power at the substrate. This 'dual source' sputtering mode uses one pulsed power source to generate a plasma in front of the target and a second, similar, source to excite a plasma in front of the substrate. This enables the deposition conditions at the substrate to be controlled independent of the sputtering conditions in a flexible and versatile manner. This offers a new and exciting means of controlling the energy delivered to the substrate during film deposition, which is a critical factor in determining the microstructures and properties of magnetron sputtered coatings. To date, this technique has been largely overlooked. We aim, therefore, to perform the first detailed study of this technique, with a view to producing ultra-high performance coatings, particularly aimed at applications such as dry machining and dry-running components, where environmental pressures to reduce the use of hydrocarbon lubricants demand coatings with properties that present technologies are struggling to deliver.We will investigate the use of dual source discharges in the enhancement and control of the ion-to-atom ratio incident at the substrate during deposition and the effectiveness of the ion etch process prior to deposition. However, in order to exploit the full potential of this new technique, it will also be necessary to undertake detailed measurements of the plasma. Thus, this study will also lead to the advancement of plasma measurement techniques in pulsed discharges. The information gained will allow us to determine the interrelationships between the driving voltage waveforms at the targets and at the substrate and the nature of the multi-excited discharge that forms, and their combined impact on film growth.