HREELS DETECTION OF RESONANCE ELECTRON-SCATTERING IN ORIENTED POLYTETRAFLUOROETHYLENE FILMS

Resonance electron scattering from surfaces of oriented polytetrafluoroethylene (PTFE) has been investigated using high-resolution electron energy loss spectroscopy (HREELS). Oriented samples were made by friction-deposition onto gold-coated silicon wafers. A resonance enhancement of the 730 cm(-1), Raman-active upsilon (C-C) stretch vibrational mode was detected near 5 eV beam energy with width of about 2 eV. The maximum intensity occurs for parallel alignment of the scattering plane with respect to the polymer chain, while no resonance is detected for perpendicular alignment. Studies were made for both specular and off-specular geometries. The origin of the resonance can be attributed to negative ion trapping into the (C-C) sigma* orbital. We have also obtained high resolutions of about 40 cm(-1) for the first time in polymer systems.