GIF Quantum enables 2D mapping of oxidation states at the atomic level
In an article entitled 2D Atomic Mapping of Oxidation States in Transition Metal Oxides by Scanning Transmission Electron Microscopy and Electron Energy-Loss Spectroscopy (Tan et al.) published in September 2011 in Physical Review Letters, the team at EMAT in Antwerp, Belgium demonstrates 2D atom by atom valence mapping in the mixed valence compound Mn3O4.
Until now, 2D fine structure analysis at the atomic level has remained challenging due to poor EELS signal-to-noise ratio and the need for simultaneous high spatial and energy resolution of the instrument. With the GIF QuantumTM ERS and its 5mm entrance aperture, a resolution of 0.4eV has been obtained with an impressive collection angle of 200mrad which allows the collection of high signal-to-noise EELS data while keeping the energy resolution high enough to differentiate Mn2+ and Mn3+ as shown in Figure d. Using STEMpack and the high speed Spectrum Imaging feature of the Quantum, the beam was scanned on the sample at high speed of 40ms / pixel to reduce sample damage while keeping a high spatial resolution with a sampling of only 0.40Å / pixel.
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For details of the lab and experimental equipment, please visit the EMAT website
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Image: Left, Map of the Mn oxidation states in Mn3O along the [100] zone axis orientation. (A) Shows the spectral weight of component A (Mn3+) and component B (Mn2+) obtained from spectrum fitting. A color map is displayed at the bottom (Red = Mn3+ , Green = Mn2+). (B) Maps after low-pass filtering. (C) Simulated maps of the Mn3+ and Mn2+ signals. Right (D) Average Mn L2,3 edge spectrum from atomic column types A (red, averaged from 24 spectra) and B (green, averaged from 54 spectra) together with references from Mn2O3 and MnO (black lines). total average Mn L2,3 edge spectrum (blue) together with a single pixel spectrum (gray) from an A-type site to demonstrate the noise level. The inset shows the HAADF signal acquired simultaneously during spectrum acquisition
Report:
2D Atomic Mapping of Oxidation States in Transition Metal Oxides by Scanning Transmission Electron Microscopy and Electron Energy-Loss Spectroscopy
Phys. Rev. Lett. 107, 107602 (2011), DOI:10.1103/PhysRevLett.107.107602
Haiyan Tan1, Stuart Turner1, Emrah Yücelen2,3, Jo Verbeeck1 and Gustaad Van Tendeloo1
1 EMAT, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerpen, Belgium
2 FEI Company, Europe NanoPort, Achtseweg Noord 5, 5651 GG Eindhoven, The Netherlands
3 National Centre for HREM, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
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Reprinted figures with permission from Haiyan Tan, Stuart Turner, Emrah Yücelen, Jo Verbeeck and Gustaad Van Tendeloo, Physical Review Letters 107, 107602, 2011. Copyright 2011 by the American Physical Society.
