Polytetrafluoroethylene (PTFE) was implanted in vacuum by N ions. The influence of experimental parameters was studied by varying ion energy from 2 to 20 keV with the same fluence of 1.4 x 10(17) ions/cm(2). The ion energy strongly affected the surface composition, microstructure, and wettability of PTFE. Five chemical bonds, CF3, CF2, CF, C-O, and elemental carbon bonds, were observed on the surface of all the as-implanted samples. The content of the various chemical bonds changed with increasing ion energy. The content of elemental carbon bond reached a maximum value of 45.81% on the surface of the sample implanted with ion energy of 5 keV. Displacement of the binding energies of the C Is peak components was observed on the surfaces of samples implanted with ion energies equal to or greater than 5 keV. Numerous microfibers drawn up in the same orientation were observed on the ion-irradiated surfaces. The droplet contact angle of the as-implanted samples increased gradually with increasing ion energy, and reached a maximum value of 117.4degrees on the surface of the sample implanted with ion energy of 20 keV. (C) 2002 Elsevier Science B.V. All rights reserved.