Visualization and characterization of ion latent tracks in semicrystalline polymers by FESEM

Abstract

This paper allows insights into how field emission scanning electron microscopy (FESEM) can be used to observe latent tracks in semicrystalline polymers and to quantitatively estimate track dimensions. The latent tracks were clearly visible on the fractured surfaces of samples subjected to controlled photooxidation. A properly chosen ultraviolet spectrum leads to polymer degradation only in the amorphous regions while the crystalline phase is nearly not affected. The latent tracks were thus visible as structureless stripes surrounded by an inhomogeneous semicrystalline matrix. The latent tracks of Kr, Xe and Bi ions in polyethylene terephthalate were found to be 28–42 nm in diameter, i.e. considerably larger than those estimated by transmission electron microscopy or small-angle scattering methods. In addition, the diameters of the amorphized zones in tracks were estimated using Fourier transform infrared spectroscopy (FTIR) by analyzing the crystalline-to-amorphous band intensity ratio as a function of ion fluence. Both the FESEM and FTIR techniques provided information on the outer track shell (a halo), thereby complementing other commonly used techniques that characterize a severely damaged central region of the ion track (a core).