Reflection electron energy loss spectroscopy (REELS) of conductive polymers obtained by keV bombardment

Abstract

Reflection electron energy loss (REELS) is used to study the modifications in the electronic structure of polystyrene. poly-2-vynilpyridine, polyethersulphone and polyimide bombarded with Ar + at 150 keV at fluences between 5 × 10 12 and 1 × 10 16 ions/cm 2. Both the bulk plasmon energy and the low-excitation energy region of the REELS spectra are strongly affected by ion irradiation. The ion beam induced spectral features for fluences up to 1 × 10 15 ions/cm 2 are close to those of hydrogenated amorphous carbons. Starting at a fluence of 5 × 10 15 ions/cm 2, Poly-2-vynilpyridine, polyethersulphone and polyimide show a drastic drop in resistivity up to value of the order of 10 −1 − 10 −2 Ω cm. The REELS spectra of these conducting samples are characterized by a peculiar step-like structure at very low excitation energy, attributable to the formation of conduction states in the pristine band-gap.