Cubic boron nitride (cBN) thin films have been deposited on silicon (100) substrate using ArF pulsed excimer laser for ablating hexagonal boron nitride (hBN) targets and a field-ionization source for activating N-2. The structure and composition of the films have been measured by Fourier transformation infrared spectroscopy (FTIR), X-ray diffraction (XRD) analysis and Auger electron spectroscopy (AES). The FTIR transmittance spectrum shows that there are a strong absorption peak at 1095.8 cm(-1) corresponding to cBN and a very weak absorption band at 1380 cm(-1) corresponding to hBN. The XRD pattern shows that there is a peak at 43.30 degrees corresponding to the cBN (111) face. These results show that the films are mainly cBN including a small amount of hBN. AES depth-profiling experiments show that the relative atomic ratio of N to B in the films is obviously increased by using a field-ionization source of about 700 V during the deposition process.