A photoemission-assisted plasma-enhanced chemical vapor deposition (PAPE-CVD) process was employed to synthesize oxygen-doped diamond-like carbon (DLC) films with low frictions for tribology application.In the PAPE-CVD process,photoelectrons emitted from a UV-irradiated substrate are utilized as a trigger for generating DC discharge plasma,resulting in a low bias voltage,a high deposition rate,a low electric power consumption,and a less frequent maintenance due to the suppression of soot on the chamber walls and electrodes[1].In this study,CO2 was mixed as a dopant gas to Ar-diluted CH4 gases during PAPE-CVD on Si(111) substrates at 150 ℃ and a total gas pressure of 200 Pa.