Observation of heavy-ion tracks in polyimide by means of high-resolution scanning electron microscopy

The etching diameter of seven-year old latent tracks created in polyimide by 7.5 MeV/A U-238 ions has been derived through high-resolution scanning electron microscopy observations and analysis according to an etching model presented herein. The diameter extracted, 6.9 +/- 1.4 nm, matches the mean width of few-weeks old latent tracks as determined recently by transmission electron microscopy. Three conclusions emerge. First, the track region that manifests itself in a highly-elevated chemical reactivity coincides with the primary structurally-altered region of the track. Second, chemical reactivity is enhanced not only by reactive alteration products but also by free volume resulted from ion-initiated processes. Third, there is no evidence of any significant healing of ion-damaged sites. (C) 2003 Elsevier B.V. All rights reserved.