Surface roughness and infra-red study of diamond-like carbon thin films

Abstract

Diamond-like-carbon (DLC) thin films were prepared on silicon and glass substrates using direct current – plasma enhanced chemical vapour deposition (DC-PECVD) from a mixture of methane, hydrogen, and argon. Two sets of samples are successfully deposited with different substrate temperatures varied from 200oC to 550oC for the first set and deposition time from 60 minutes to 180 minutes for the second set of sample, while maintaining other important deposition parameters. The films thickness is determined by using a conventional ellipsometer, the morphology of the films has been analyzed by using Atomic Force Microscope (AFM) and the structure of the films is studied by using FT-IR spectroscopy. The thickness analysis shows that the thickness of DLC thin films is decrease as the substrate temperature increase but increasing as the deposition time increase for both glass and silicon substrate. The AFM results show high rms roughness at 550oC for glass substrate and 300oC for silicon substrate; meanwhile both of substrate materials show a high rms roughness at 120 minutes deposition time. The transition temperature is suggested to be 400oC for glass substrate and 550oC for silicon substrate. The growth mechanism is explained base on subplantation model. The IR spectra show that both set of sample contain a lot of sp3 clusters but hydrogen is still present in each sample. The degree of absorption is also enhanced by the reduction of substrate temperature and deposition time.