Electron Irradiation of Poly(3-hexylthiophene) Films

The effects of low-energy electron irradiation on spin-coated films of regioregular poly(3-hexylthiophene) have been studied with fluorescence, mass spectrometry, and a variety of electron spectroscopies, including photoemission. Electron impact by 180 eV electrons causes a decrease in photoluminescence intensity, broadening of the thiophene ring valence electronic state features, and diminution in intensity of the peaks due to π electrons delocalized along the backbone. Electron bombardment also results in a decrease in the X-ray photoelectron spectroscopy sulfur-to-carbon ratio, but only minor shifts in the binding energies of the C 1s and S 2p peaks occur. Quadrupole mass spectrometry has been used to detect electron-stimulated desorption from the polymer films. Ionic desorption includes S -, SH -, S +, and C x H y + species. Auger electron spectroscopy confirms removal of sulfur from the near-surface region by a 5 keV electron dose of 1.8 × 10 18 electrons/cm 2, and electron energy loss spectroscopy suggests formation of a graphitic surface.