Control of the size of etchable ion tracks in PVDF – Irradiation in an oxygen atmosphere and with fullerene C60

Abstract

We pursue the possibility of controlling the size of etchable ion tracks of poly(vinylidene-fluoride) (PVDF) films. At first, 330 MeV 40Ar ions were irradiated to a 25-µm-thick PVDF film in oxygen using the uniform-beam formation/irradiation system at Takasaki Ion Accelerators for Advanced Radiation Application (TIARA) cyclotron of National Institutes for Quantum and Radiological Science and Technology (QST, Japan). Compared with the irradiation in a high vacuum, which is the conventional method, it is clear that more oxygen-containing functional groups are formed on the surface, the size of the pores becomes larger and the track-etching rate is accelerated. The result shows that the irradiation in oxygen effectively induces oxidation of ion tracks and the oxidation widens the size of the etchable ion tracks. Next, we attempted the irradiation with 6-MeV fullerene C60+ ions. Compared with the irradiation with 100-keV C+ monatomic ions of the same velocity, the fullerene-ion irradiation induced large sized etchable tracks on the surface of PVDF. The result could represent the effect of local and simultaneous collisions by the aggregated ions. Both of the irradiations showed widening the size of etchable ion tracks and we were able to control the pore diameter by varying the etching time.