Characterization of insulators by high resolution electron energy loss spectroscopy: application of a surface potential stabilization technique

A surface-potential stabilization technique is described which permits one to take vibrational spectra of excellent quality with high-resolution electron-energy-loss spectroscopy on insulating samples of very different types, such as ionic insulators and polymers. Induced surface conductivity and enhanced secondary-electron emission close to the vacuum level are found to be at the origin of the surface-potential stabilization, which is done by irradiation of the sample with electrons in the keV range. Nonequilibrium carrier densities and mean free paths are estimated from observable Drude damping. Irradiation effects are discussed.