From pulsed-DCMS and HiPIMS to microwave plasma-assisted sputtering: Their influence on the properties of diamond-like carbon films

The fabrication of high-hardness non-hydrogenated diamond-like carbon (DLC) via standard magnetron sputtering (MS) is often hindered by the low sputtering yields and ionisation rates of carbon, therefore investigations into pulsed alternatives of MS, else sputtered species post-ionisation methods, are of particular interest. This work focuses on investigating the influence of pulsed-direct current MS (pDCMS), high power impulse magnetron sputtering (HiPIMS) and their microwave plasma-assisted (MA-pDCMS, MA-HiPIMS) variants on the properties of the fabricated DLC films. Two setups were used for the pDCMS-and HiPIMS-based methods, respectively. The films were characterised using Raman spectroscopy, nanoindentation, X-ray reflectometry and scanning electron microscopy, where the pDCMS-produced films were additionally characterised by film-stress measurements. Moreover, in situ time-resolved Langmuir probe plasma analysis was performed under HiPIMS and MA-HiPIMS conditions to analyse the influence of the magnetron and microwave plasmas on one another. For both DCMSand HiPIMS-based procedures, it was found that the addition of microwave plasma did not facilitate attaining hardnesses beyond 30 GPa, however, it did enable modifying the morphology of the films. Furthermore, this study shows the potential of synchronised sputtering with substrate biasing, as well as the importance of microwave plasma source positioning in relation to the substrate.

Automated summary

This study investigates the influence of different magnetron sputtering methods and microwave plasma-assisted techniques on the properties of high-hardness diamond-like carbon films, and it is found that microwave plasma can modify the morphology of the films but cannot increase the hardness.