Oral Presentation 26th ACMM “2020 Visions in Microscopy”

Mapping for atomic-site-specific oxidation states of metal atoms by EELS with STEM-moiré method (#82)

Eiji Okunishi 1
  1. JEOL Ltd., Akishima, TYO, Japan

In STEM, two-dimensional moiré pattern can be obtained with controlled pixel intervals whose pitch correspond to single or multifold spacing of sample lattice fringes. Recently, we reported the pseudo atomic column elemental map using this STEM Moiré method [1]. An advantage of this method is low dose because a pixel interval is 10 to 20 times longer than that in conventional atomic column elemental mapping [2]. With such a sparse pixel interval, average dose density on a sample is drastically reduced to 1/100 or less than in the conventional method. With this method, we have already succeeded in observing a pseudo atomic column elemental map for a fragile mineral sample such as Aquamarine [3]. In this paper, we tried to visualize the difference of valence states of Mn atoms in Mn3O4 by mapping using EELS of this method at low dose condition, which was reported by conventional method [4]. In the result, atomic columns of Mn2+, Mn3+ and O2- are observed in distinguished atomic columns. we can conclude that the STEM moiré method at low dose is suitable for mapping of oxidation state of metal atoms, since the oxidation state may be more changeable than substitution of atomic species. And the result by this STEM moiré method encourages to try 2D-mapping of atomic state for very fragile samples.