With development of optical. recording media oriented toward high-density optical systems, the protection of data storage becomes very critical. In this article, we report on the diamond-like carbon (DLC) films deposited by plasma-enhanced chemical vapor deposition on the polycarbonate (PC) substrate of phase-change optical recording disks. The mixed SiH4 in CH4/H-2 gases were used to reduce the internal compressive stress of the deposited films. The structural characteristics of the DLC films were analyzed as a function of film thickness by Raman spectroscopy. The variations of the G peak positions and the intensity. ratio, I-D/I-G, were investigated as a function of the DLC film thicknesses. The DLC film thickness is a very important characteristic related to the surface microroughness and transmittance. Several tests, including a tape pull test, a thermal shock test, and an alcohol rub test, were used to evaluate the adhesion of the DLC coatings on the PC substrates. The rms roughness and morphology of DLC films were inspected by an atomic force microscope. The dependence of optical transmittance, reflectivity, and the overwriting characteristics of jitter on the thickness of DLC films were investigated. Finally, our results indicate that DLC films can provide an effective capability for protecting stored data and exhibit a smooth enough surface and high transparency quality for the recording and overwriting characteristics of phase-change optical disks. (C) 2005 American Vacuum Society.