Enhanced nucleation and large-scale growth of CVD diamond via surface-modification of silicon-incorporated diamond-like carbon thin films

Abstract Herein we report a method to tailor the surface of silicon-incorporated diamond-like carbon (Si-DLC) thin films to enhance the diamond nucleation density and growth. In this technique, the surfaces of Si-DLC films were modified by fluorine and oxygen species utilizing a reactive-ion etching (RIE) method. The surface properties of Si-DLC, oxygen-terminated Si-DLC (O Si-DLC), and fluorine-terminated Si-DLC (F Si-DLC) films were investigated and compared. The analyses depicted that the sp2/sp3 ratio of carbon‑carbon bonds has diminished from 20.28% for Si-DLC film down to 8.96% and 4.41% for O Si-DLC and F Si-DLC films, respectively. Moreover, a significant amount of new sp3 hybridized bonds formed on the surface of the modified Si-DLC thin films, particularly in F Si-DLC film. The deposition of micro-diamond on the films was performed using hot filament chemical vapor deposition (HFCVD). SEM, XRD, and Raman results showed the enhancement in nucleation density and growth of micro-diamond on F Si-DLC and O Si-DLC films and the in-plane stress reduction up to 60%. Owing to the lower number of sp2 bonds and the greater number of new sp3 sites, the F Si-DLC thin film provided a superior platform for diamond nucleation than O Si-DLC film. The continuous diamond coverage on F Si-DLC film was up to ~2 mm2 versus ~0.4 mm2 for O Si-DLC film.