Valence state mapping of cobalt and manganese using near-edge fine structures

The properties of transition metal oxides are related to the presence Of el ements with mixed valences. The spectroscopy analysis of the valence,states is feasible experimentally, but a spatial mapping of valence states of tra nsition metal elements is a challenge to existing microscopy techniques. In this paper. with the use of valence state information; provided by the whi te lines and near-edge fine structures observed using the electron energy-l oss spectroscopy (EELS) in a transmission electron microscope (TEM), a nove l experimental approach is demonstrated to map the valence state distributi ons of Mn and Co using the ratio of white lines in the energy-filtered TEM. The valence state map is almost independent of specimen thickness in the t hickness range adequate for quantitative EELS microanalysis. An optimum spa tial resolution of similar to 2 nm has been achieved for a two-phase Co oxi des. (C) 2000 Elsevier Science Ltd. All rights reserved.