We report deposition of diamondlike carbon (DLC) films on silicon substrates in vacuum by ablating a graphite target using KrF excimer laser. High voltage pulses synchronous with the ablating laser pulse were applied to substrates to improve the hardness and adhesion of the DLC film. Ions accelerated in the carbon plasma plume resulted in an increase of ion flux and energy that modified the film properties. The effect of high voltage pulses on the laser ablated plasma plume was investigated by the laser induced fluorescence method, and their effect on DLC films was examined using Fourier transform infrared atomic force microscopy, and nanoindentation. High voltage pulse applied to the substrate increased the sp(3) constituent in the DLC film and enhanced the smoothness and hardness of the film.