Berlin 2008 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 46: Interfaces

MM 46.4: Talk

Thursday, February 28, 2008, 17:15–17:30, H 0111

ELNES at internal metal-oxide interfaces — •Oliver Heckl¹ and Ferdinand Haider² — ¹ETH Zürich, Institute of Quantum Electronics, Wolfgang-Pauli-Str. 16, 8093 Zürich — ²University of Augsburg, Institute of Physics,Universitätsstr. 1 , 86135 Augsburg

The heterophase boundaries between precipitates such as spherical amorphous SiO₂ particles inside a copper matrix as well as crystalline CuO precipitates inside a silver matrix and the surrounding metal matrix are examined with high spatial resolution using a scanning transmission electron microscope (STEM) equipped with an electron energy loss spectrometer (EELS). Typical features of the electron energy loss near-edge fine structure (ELNES) of the oxygen K ionization edge allow to determine the bonding state of oxygen and thus to detect interlayers at the phase boundary. The validity of Kirchheim’s structural vacancy model of oxygen segregation at metal-oxide interfaces is verified this way. It predicts that no interfacial accumulation of excess oxygen occurs at the phase boundary of amorphous precipitates. For the Ag-Cu alloy there is the additional degree of freedom for the oxidation value of copper and it can be seen that structural vacancies change the oxidation value at the phase boundary.