A study of structural and spectral properties of ion-beam modified polyethylene terephthalate membrane

Highlights: • Modification of the structure of PET membrane exposed to 100 keV N⁵⁺ ions at varying fluence. • Changes in optical and dielectric properties were analyzed. • The ion implantation caused decreasing value of E_g from 3.75 eV to 0.38 eV. • Sample treated with 10¹⁶ cm⁻¹ was carbonized, becoming a similar to amorphous carbon. -- Abstract: In this study, we investigated a modification of the structure of polyethylene terephthalate (PET) membrane exposed to 100 keV N⁵⁺ ions with fluences varying from 10¹⁴ to 10¹⁶ ions/cm². The changes in the properties of the ion-beam modified samples of PET membrane were analyzed by Fourier transform infrared (FTIR) spectroscopy, ultraviolet–visible (UV–Vis) and dielectric spectroscopies. FTIR spectra showed a change in the intensity of the typical bands after the irradiation of the polymers. The results of the optical measurements showed that the increase in the ion irradiation fluence induced a decrease in the transmittance of the PET membrane. The estimated value of the energy band gap decreased with the increase of the fluence. A significant decrease of the energy band gap was observed for the ion beam fluence of 10¹⁶ ions/cm². The dielectric measurements performed in a wide frequency band in the range from 20 Hz to 10 MHz and temperature range from 120 K to 400 K revealed that ion beam treatment with a fluence of 10¹⁶ ions/cm² changed the characteristic temperature dependence of the dielectric loss tanδ (T).