Characterization of hydrogen-free diamond-like carbon film deposited on cyclic olefin copolymer

In this study, the feasibility of the diamond-like carbon (DLC) film as a viable component for cyclic olefin copolymer (COC) substrate overcoat was assessed. Featured by its advanced physical and chemical properties such as high hardness, chemical stability, and wide band-gap optical transparency, the hydrogen-free DLC exhibits promising characteristics as the overcoat for flexible substrates or other TFT components. Ultra smooth, DLC thin films were synthesized by using a filter arc deposition (FAD) system and a cathodic arc evaporation (CAE) system. Raman spectroscopy, ESCA, Nano-Indentation, and electron microscopy were used to characterize the electronic, morphological, and microstructure properties of the DLC coatings. Results indicate that the device-quality DLC needs to be synthesized at lower substrate bias potential to retain high sp3/sp2 ratio. The bending tests demonstrated a 30-fold improvement of the DLC-protected COC over that of the unprotected COC. Water vapor permeability tests demonstrated a 25-fold improvement of the DLC-protected COC over that of unprotected COC.