Influence of the substrate bias potential on the properties of ta-C coatings deposited using Venetian blind plasma filter

• ta-C films were deposited by pulsed arc method using a Venetian blind plasma filter.
• Dependence of the film properties on the substrate bias potential was studied.
• Substrate bias determines the content ratio of sp3 and sp2 phases in the ta-C films.
• Substrate bias influences the roughness, microhardness, and adhesion of the films.

The paper presents the research results on the formation of amorphous ta-C films with a minimum amount of defects, deposited by pulsed vacuum-arc method with the use of a water-cooled electromagnetic Venetian blind plasma filter. The subject of the research was the influence of the substrate bias voltage, in the range of − 25 to − 200 V, on the structural and mechanical properties of ta-C coatings. Dependence of the microstructure and phase composition of ta-C films on the substrate bias voltage were analyzed by Raman and X-ray photoelectron spectroscopy. The results of the structural analysis of coatings showed characteristic changes in the content of the diamond-like sp3 fraction on the substrate potential. Mechanical properties of ta-C films — roughness, adhesion, hardness and Young's modulus were investigated using a profilometer, the scratch tester and a nanoindenter. The highest content of sp3 bonds, of about 63%, was obtained in the coating deposited at the substrate bias potential of − 100 V, which also showed the minimum surface roughness and maximum hardness and Young's modulus of 50 GPa and 371 GPa respectively. The ta-C coating synthesized at this bias potential had excellent adhesion — complete film delamination occurs at the load of 41 N. Our preliminary studies and the results described in this work enable the use of electromagnetic Venetian blind plasma filter for deposition of thin ta-C coatings with a minimum amount of defects.