After analyzing the molecular structure of several organic solvents we select methanol, N,N-dimethylformamide (DMF) and acetonitrile as the carbon source to deposit diamond-like carbon (DLC) films on Si plate with a pulse-modulated power. The deposition reaction can be facilitated by increasing temperature or by decreasing separation between the electrodes. The films were characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy and Raman spectroscopy sequentially. The results showed that the films were typical hydrogenated DLC films. Hydrogen was removed and the primary bonding in the films changed gradually from sp3-bonded carbon to sp2-bonded carbon as annealing proceeded, i.e. the film underwent a graphitization process. Comparing the results of different solvents, we discover that the methyl group of the solvents seems to be the functional group in forming the DLC films.