Field emission from individual tips in n- and p-type silicon field emitter arrays (FEAs) has been directly evaluated by using an electrostatic lens projector. The number of the emission spots in the p-type FEA increased with increasing total emission current, and the p-type FEA exhibited better uniformity of the emission than the n-type FEA. In order to improve the emission uniformity, the operation of the FEAs under an atmosphere of ambient gas was executed. The emission uniformity was improved dramatically by exposing C₂H₄ gas. Also, surface modification of Si field emitters was investigated for damageless vacuum sealing. The vacuum sealing process reduced the emission currents from the nontreated Si FEA by a factor of 10. On the contrary, the emission current from the CHF₃-plasma-treated FEA did not change before and after the vacuum sealing process.