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 pi 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 CxHy+ species. Auger electron spectroscopy confirms removal of sulfur from the near-surface region by a 5 keV electron dose of 1.8 x 10(18) electrons/cm(2), and electron energy loss spectroscopy suggests formation of a graphitic surface.