Gated Si field emitter arrays (FEAs) have been operated in various gas atmospheres such as air, H-2, O-2, and Ar at 10(-7) Torr to improve the emission behavior. The electron emission from the FEAs was enhanced by a factor of up to 10 during or after gas ambient emission with H-2, O-2, and Ar, while the improvement was not observed by a process with air. Fowler-Nordheim plots indicated a drastic change in slope only for H-2 processes, in which hydrogen atoms would adsorb to Si tip surfaces. An emission pattern with a fourfold symmetry was observed for a single-tip emitter after hydrogen ambient emission, indicating the tip surface crystallinity after gas ambient emission.