Field emitters of vertical carbon fibers on a silicon substrate are fabricated by catalytic chemical vapor deposition. After an ageing process of 150 min, field emission measurement of the fibers is carried out in a vacuum chamber with a base pressure of 5.0 x 10(-4) Pa. The experimental results display that field emission performance of the carbon fibers depends strongly on the vacuum level during the experiments. After the field emission measurement, damage to the carbon fiber field emitters is observed from the scanning electron microscopic images. (c) 2007 Elsevier B.V. All rights reserved.