Tuning Diamond and Diamond-Like Carbon Film Growth via Copper Nanolayer Thickness in PECVD

We present a systematic investigation of copper nanolayer thickness as a critical parameter controlling diamond film formation via plasma-enhanced chemical vapor deposition (PECVD). By examining Cu interlayers from 10-80 nm on silicon substrates, we demonstrate a direct correlation between Cu thickness and diamond-like character in carbon films. Field emission scanning electron microscopy reveals morphological transitions from spherulite-like structures to faceted grains with increasing Cu thickness. Raman spectroscopy shows progressive ID/IG ratio reduction, while X-ray photoelectron spectroscopy confirms remarkable sp³ carbon enhancement from 14% to 34%. Tribological analysis reveals contrasting behavior: 10 nm Cu interlayers with continuous amorphous/DLC films exhibited higher friction coefficients (~0.18-0.20) but superior wear resistance, while 80 nm Cu with faceted diamond grains showed lower friction (~0.15-0.18) accompanied by deeper wear tracks. Notably, our findings indicate Cu nanolayers influence extends beyond physical surface parameters, suggesting significant chemical interactions between Cu and carbon atoms during nucleation and growth. This study introduces a novel approach to diamond synthesis at reduced temperatures without conventional seeding, offering new possibilities for controlling carbon film properties through strategic interlayer engineering—a breakthrough for advanced coating applications.