6.2.2.3 Insulators and oxides

This chapter provides information on inelastic scattering of electrons in insulators and oxides. Insulators may be studied by electron energy loss spectrum (EELS) at primary energies for which the secondary electron yield is unitary or by neutralizing the sample by flooding it with an auxiliary electron gun. An electronic transition is present at ≈4 eV loss energy on (1100) surface which shows a strong azimuthal anisotropy. The measured and calculated frequencies of the Fuchs-Kliewer phonons of various intrinsic materials are tabulated. Surface and superconducting properties of superconducting oxides were studied with low energy EELS on YBa₂Cu₃O₇ and Bi₂Sr₂CaCu₂O₈ single crystals cleaved under vacuum. On YBa₂Cu₃O₇ a loss feature associated with the energy gap was observed. On Bi₂Sr₂CaCu₂O₈ two modes were observed at 51 meV and 81 meV on low conductivity areas. EEL-spectra and probability of n-phonon excitation of ZnO(1100) is illustrated. Loss probability for the surface phonon on MgO(001) is figured out. HREEL-spectra for Bi₂Sr₂CaCu₂O₈ and YBa₂Cu₃O₇ are shown.