Extension of lifetime of silicon field emitter arrays (Si-FEAs) in oxygen ambient was achieved by implanting carbon negative ions into the emitter surface. The authors examined three samples, each of which has 1024 field emission tips and implanted with 5 keV carbon negative ions to the doses of 1 x 10(16), 3 x 10(16), and 1 x 10(17) ions cm(-2). The lifetime, the time when the emission current becomes half the maximum value after starting operation, was extended in accordance with the implantation dose. The lifetime of the sample which was dosed with 1 x 10(17) ions cm(-2) was 50 h, which was about 17 times as long as that of as-fabricated Si-FEA. (c) 2008 American Vacuum Society.