Three dimensional mapping of Fe dopants in ceria nanocrystals using direct spectroscopic electron tomography.
Electron tomography is a powerful technique for the 3D characterization of the morphology of nanostructures. Nevertheless, resolving the chemical composition of complex nanostructures in 3D remains challenging and the number of studies in which electron energy loss spectroscopy (EELS) is combined with tomography is limited. During the last decade, dedicated reconstruction algorithms have been developed for HAADF-STEM tomography using prior knowledge about the investigated sample. Here, we will use the prior knowledge that the experimental spectrum of each reconstructed voxel is a linear combination of a well-known set of references spectra in a so-called direct spectroscopic tomography technique. Based on a simulation experiment, it is shown that this technique provides superior results in comparison to conventional reconstruction methods for spectroscopic data, especially for spectrum images containing a relatively low signal to noise ratio. Next, this technique is used to investigate the spatial distribution of Fe dopants in Fe:Ceria nanoparticles in 3D. It is shown that the presence of the Fe2+dopants is correlated with a reduction of the Ce atoms from Ce4+towards Ce3+. In addition, it is demonstrated that most of the Fe dopants are located near the voids inside the nanoparticle.
EMAT, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium.
Bart
B
Goris
EMAT, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium.
Maria
M
Meledina
EMAT, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium.
Stuart
S
Turner
Centrum Wiskunde & Informatica, P.O. Box 94079, 1090 GB Amsterdam, The Netherlands.
Zhichao
Z
Zhong
Centrum Wiskunde & Informatica, P.O. Box 94079, 1090 GB Amsterdam, The Netherlands; Mathematical Institute, Leiden University, Niels Bohrweg 1, 2333CA Leiden, The Netherlands.
K Joost
KJ
Batenburg
EMAT, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium.
Sara
S
Bals
Ceria nanoparticles; Dopants; EELS; Electron tomography; Spectroscopy; Valency