A paradigm shift in thin film growth by magnetron sputtering: towards metal-ion-controlled process

Important results from the project

The project aimed at developing new processing routes for high-quality coatings at reduced substrate temperatures. This implies a paradigm change in thin film growth by magnetron sputtering by replacing traditionally used gas-ion irradiation with that by metal-ions. We showed that the mass of incident metal ions plays a crucial role for the quality of coatings deposited with no external heating. We obtained hard and dense TiAlWN coatings at substrate temepratures not higher than 130 °C (as compared to typically used 400-500 °C). The process energy consumption was lowered by 65%.

Expected long term effects

Coatings deposited with Cr+ irradiation (TiAlCrN) exhibited porous nanostructure, high oxygen content and poor mechanical properties. In contrast, TiAlWN films were fully-dense even with the lowest W concentration, showed no evidence of hexagonal AlN precipitation, and exhibited mechanical properties typical of TiAlN grown at 500 °C. Thus, our new film growth concept allows to substitute the thermally-driven adatom mobility with that supplied by effective low-energy recoil creation by heavy metal ion irradiation. The process energy consumption is lowered by 65%.

Approach and implementation

Three series of TiAlMeN films (Me = Cr, Mo, or W) were grown by a combination of DC and HiPIMS sputtering with no external heating resulting in that the substrate temperature did not exceed 130 °C during growth (typically 400-500 °C is used in industry). The effect of metal ion mass was studied (varied from 52.0 amu for Cr to 183.8 amu for W). Results showed very conclusively that irradiation with lower mass ions does not produce high quality TiAlCrN coatings irrespective of Cr dose. In contrast, as little as 5 at.% of W supplied in the form of W+ enables deposition of dense and hard TiAlWN layers.