GaN thin films were deposited on Si substrates using do sputtering method and characterized-with various methods. X-ray diffraction, transmission electron microscopy, and selected-area electron diffraction measurements show that the GaN thin film is amorphous with nanocrystalline grains. Fourier transform infrared indicates that the absorptive properties of the deposited GaN film exhibit primarily Ga-N stretching vibration bond. Atomic force microscopy shows that there are many sharp tips on the surface. The GaN thin film containing nanocrystalline grains demonstrates very good field emission properties with the turn-on field of 5 V/mu m and the maximum current density of 500 mu A/cm(2). The possible emission mechanisms of the films are also discussed. (c) 2006 American Vacuum Society.