A strategy to enhance the electron temperature in modulated pulsed power magnetron sputtering (MPPMS) discharges for the deposition of diamond-like carbon thin films

Abstract The introduction of neon (Ne) into argon (Ar) plasma has been shown to enhance electron temperature, offering a promising method for depositing diamond-like carbon (DLC) thin films directly from a graphite target. In this study, helium (He) is introduced into Ar gas to deposit DLC thin films using modulated pulsed power magnetron sputtering since He exhibits the highest initial ionization energy at 24.58 eV of all noble gases. Results indicate that the presence of He enhances the deposition rate compared to pure Ar conditions. Specifically, when the He flow rate exceeds 30%, the deposition rate nearly doubles, resulting in DLC thin films predominantly exhibiting a dense columnar microstructure. However, the morphology of thin films gradually transits from dense columnar structures to much porous characteristics with the introduction of He. Analysis of the I D / I G ratio reveals that the sp 2 /sp 3 bonding ratio of the DLC thin films is directly influenced by the He flow rate, with the highest sp 3 bonding fraction achieved at a He flow rate of approximately 60%. A comprehensive global model is established to compare the discharge plasma characteristics of Ar–C and He–C. Our findings demonstrate that He–C discharge plasma exhibits higher electron temperature and C atom ionization rate in plasma, which likely plays a significant role in manipulating the microstructure and properties of DLC thin films.