Fabrication of ion-track-etched pores on fluoropolymer by heavy ion beam irradiation in an oxygen atmosphere

Kitamura, Akane; Yamaki, Tetsuya*; Yuri, Yosuke*; Koshikawa, Hiroshi*; Sawada, Shinichi*; Yuyama, Takahiro*

Ion track membranes of polyvinylidene fluoride (PVDF) are produced by chemical etching using a strong oxidant in an alkali solution after irradiation with an ion beam in vacuum. The oxidant erodes not only ion tracks but also a pristine surface of PVDF. Therefore, it causes serious deterioration in the quality of PVDF membranes. We have developed a track etching technique without any oxidant by irradiation with an ion beam in an oxygen atmosphere. PVDF films were irradiated with 330-MeV Ar ions in an oxygen atmosphere using a uniform-beam formation/irradiation system developed at the TIARA AVF-cyclotron facility. The maximum etching rate resulting from the present method was six times faster than that from the conventional method; furthermore, the maximum diameter of track-etched pores with the present method was more than twice as large as that in the conventional method. This suggests that the irradiation in oxygen can provide a useful technique of an oxidant-free track-etching process.