Structural and mechanical properties of diamond-like carbon films prepared by pulsed laser deposition with varying laser intensity

Diamond-like carbon (DLC) films have been prepared by pulsed laser deposition (PLD) (wavelength 248 nn), ablating highly oriented pyrolytic graphite (HOPG) at room temperature in a vacuum of 10(-2) Pa, at fluences between 0.5 and 35 Jcm(-2). Films have been deposited on Si(100) with and without a SiC interlayer. Structural analysis, such as visible and UV Raman, Infrared and Electron Energy Loss (EEL) spectroscopies show that the films are hydrogen-free and undergo a transition, from mainly disordered graphitic to up to 80% tetrahedral amorphous carbon (ta-C), above a laser threshold fluence of 5 J cm(-2). The measured residual stresses of as deposited ta-C films do not exceed 2 GPa. Scratch tests show excellent adhesion properties. Low friction coefficients (0.05-0.1) have been measured in ambient humidity. Nanoindentation indicates that film hardness is as high as 70 GPa.