Fourier transform infrared and ultraviolet-visible investigation of swift heavy 100 MeV Ag-ion- and 75 MeV oxygen-ion-irradiated polyvinylidene fluoride thin films

Abstract

Polyvinylidene fluoride (PVDF) polymer films (9, 12, and 20 μm) were irradiated with 100 MeV Ag ion (fluence: 1.875×10¹¹ ions/cm²) and 75 MeV oxygen ion (fluences: 5.625×10¹¹ and 5.675×10¹² ions/cm²) using the PELLETRON facility at the Inter University Accelerator Centre, New Delhi, to study swift heavy ion (SHI) irradiation effects in thin films. The change in chemical, optical, and structural properties was analysed by comparing Fourier transform infrared (FTIR) and ultraviolet (UV)-visible spectra of pristine and irradiated films. The FTIR spectra show no major change in characteristic bands on irradiation, except that some weak bands appear because of the evolution of volatile species, unsaturated bond formation, decomposition of the free radicals, and subsequent cross-linking. The spectra of the irradiated films show some broadening and a decrease in intensity in characteristic bands when compared with the pristine samples. The FTIR results indicate that the overall chemical structure of PVDF is stable under SHI irradiation.

The UV-visible absorption spectra of irradiated samples reveal hyperchromic shift, bathochromic shift, and hypsochromic shift. The spectra also estimate the direct optical band gap around 3.6 eV. The band gap decreases on irradiation, and the decrease is dependent on ion beam and fluence rate. The present study opens up the scope for the applicability of SHI-irradiated PVDF thin films as microsensors and actuators.