A HRTEM and EELS study of Pd/ZnO polar interfaces

Atomic and electronic structures of interfaces in an internally oxidized Pd/ZnO system were studied by high-resolution transmission electron microscopy (HRTEM) and electron energy-loss spectroscopy (EELS). {0001}ZnO polar planes tend to be parallel to the interface. A ZnO precipitate was terminated by an oxygen surface at one end of the precipitate and by a zinc (0001) surface at the other end of the precipitate. A pre-edge peak was detected only in O-K energy-loss near-edge spectra (ELNES) acquired from the oxygen-terminated interface. Ab initio calculations indicated that the origin of the pre-edge peak could be attributed to the strong chemical bonding and hybridization of Pd-d and O-p orbitals at the oxygen-terminated polar interface.