LET dependence on the track etch rate in ion irradiated polyimide films

Koshikawa, Hiroshi; Asano, Masaharu*; Yamaki, Tetsuya; Maekawa, Yasunari

We investigated track etch rates (V) of polyimide irradiated with different ions by a conductivity technique and their LET dependence. Both of 12 and 25 m thick films were irradiated with 450 MeV Xe, 250 MeV Ar and 75 MeV Ne and then were etched with a sodium hypochlorite solution. The conductometric analysis involves recording electric conductance of the etchant across the film during the etching time. When the etched pores from both sides of the film made contact with each other, the conductance suddenly increased to find the breakthrough time (T). A V value was obtained by dividing the half thickness of the films by T. The Xe ions with the highest LET of 12 MeV/m gave ca. 20 times higher V than the Ne ions. The change in V for the different beams is ascribed to an LET effect by considering that the bombardment with high-LET ions produces more severe molecular damage in each track.