On the penetration of etchant into tracks in polycarbonate

The time dependence of the uptake of NaOH/LiOH etchant in pristine polycarb onate (PC) and in PC irradiated with 3 GeV Pb ions has been examined. Diffe rent stages of etchant penetration can be distinguished. The overall surfac e-near etchant uptake along tracks is always higher than the the one of the nonirradiated pristine material. Furthermore, the directional dependence o f the etchant penetration during the incubation time is studied. Though the shapes of the etchant distributions along the tracks are practically the s ame in all directions, they differ in their absolute magnitudes. This can b e explained by the different cross-sectional track areas exposed at the sur face, which enable different etchant penetration efficiencies. Therefore, t racks which run more or less parallel to the surface normal show less etcha nt uptake than those being strongly tilted. (C) 2000 Elsevier Science Ltd. All rights reserved.