In this paper, nanocrystalline Si MOS cathodes are fabricated by laser ablation technique. This is the first step to understand the emission mechanism of nanocrystalline-based cathodes because the technique is appropriate for fabricating nanocrystalline Si covered with a thin oxide layer. Results show that electron emission occurred nearly at a gate voltage of 6 V, which is as low as the work function of the Au gate electrode. The emission current and the efficiency defined as the ratio of the emission current to the total tunneling current flowing through the diode are higher for a thinner metal, indicating that tunneling is sensitive to metal thickness