We have fabricated single-atom field emission (FE) tips by annealing Rh-deposited W tips at 900 K, and the FE characteristics were investigated. Due to the formation of the nanotips, the electron beams were confined in a semi-cone, angle of 3 degrees, an indication quite different from the conventional FE beams. In repairing-function test where the FE nanotips were intentionally destroyed beforehand, they recovered the peculiar FE characteristics by means of feasible low temperature annealing. Finally, we found that the present nanotips equipped the capability of recovering the unique FE properties even after an exposure to the air. These characteristics are significantly relevant to the practical applications to electron-optics instruments. (c) 2005 Published by Elsevier B.V.