Influence of radial distance from plasma stealth center on nano-mechanical and hydrophobic characteristics of diamond-like carbon/cu composite films synthesized via PECVD

This study investigates how radial distance from the plasma stealth center influences the nano-mechanical and hydrophobic properties of diamond-like carbon (DLC)/Cu composite films produced via plasma-enhanced chemical vapor deposition (PECVD). Optimized process parameters were used to deposit Cu/DLC layers on stainless steel, combining RF-PECVD and RF-sputtering. Raman and FTIR analyses revealed changes in the ID/IG and sp2/sp3 ratios across positions up to 100 mm from the plasma center. As distance increased, the ID/IG ratio decreased from 0.695 to 0.540, while the sp2/sp3 ratio increased from 0.595 to 0.925. Nano-mechanical properties were evaluated at various loads (5, 10, 15, and 20 mN), showing that greater loads resulted in increased penetration depth. At a 5 mN load, hardness measurements showed a decrease from 26.5 GPa to 16 GPa as the distance from the plasma stealth increased. Similarly, Young's modulus dropped from 240 GPa to 211 GPa. Hydrophobicity decreased with distance, as the water contact angle dropped from 100 degrees directly below the plasma stealth to 75 degrees at 100 mm. These findings demonstrate the significant impact of radial distance from the plasma center on both the structural and mechanical properties of the films.