Electron vibrational spectroscopy of thin polyimide films

We describe high resolution electron energy loss (HREELS) and UV-photoemission (UPS) measurements performed to investigate the vibrational and electronic surface and interfacial properties of thin insulating polymer films. The measurements were performed in ultrahigh vacuum on PMDA–ODA films of thicknesses ∼30–50 and ∼1000 Å which were spun onto silicon or onto metallic substrates and on thin PMMA films deposited on metallic substrates. The general characteristics of our HREELS spectra are weak, diffuse electron scattering and broad vibrational bands which we have assigned by comparison to infrared absorption data. Cooling the polymer films which were spun onto Si substrates to ∼100 K resulted in a uniform reduction of the overall spectral broadening. This additional inelastic scattering contributing to the broadening appears to originate at the PMDA–ODA/Si interface.