EEL spectroscopic tomography: Towards a new dimension in nanomaterials analysis

Abstract

Electron tomography is a widely spread technique for recovering the three dimensional (3D) shape of nanostructured materials. Using a spectroscopic signal to achieve a reconstruction adds a fourth chemical dimension to the 3D structure. Up to date, energy filtering of the images in the transmission electron microscope (EFTEM) is the usual spectroscopic method even if most of the information in the spectrum is lost. Unlike EFTEM tomography, the use of electron energy-loss spectroscopy (EELS) spectrum images (SI) for tomographic reconstruction retains all chemical information, and the possibilities of this new approach still remain to be fully exploited. In this article we prove the feasibility of EEL spectroscopic tomography at low voltages (80 kV) and short acquisition times from data acquired using an aberration corrected instrument and data treatment by Multivariate Analysis (MVA), applied to Fe(x)Co((3-x))O(4)@Co(3)O(4) mesoporous materials. This approach provides a new scope into materials; the recovery of full EELS signal in 3D.

Applications of exchange coupled bi-magnetic hard/soft and soft/hard magnetic core/shell nanoparticles

“…By acquiring EELS spectrum images (SI) in a TEM at different tilt angles (i.e., tomography), it is possible to obtain a 3D reconstruction of the elemental distribution in the material. For instance, EELS-SI tomography has been used to chemically determine the 3D structure of Co 3 O 4 /Fe x Co (3-x) O 4 core/shell mesoporous particles down to pore resolution [217].…”

Linear chemically sensitive electron tomography using DualEELS and compressed sensing

“…Whilst X-rays and EFTEM mainly allow the mapping of elemental contents, EELS offers additional possibilities for studying detailed chemistry. Early studies have already shown the feasibility of EELS-STEM tomography [2,3]. Nevertheless, EELS suffers significantly from multiple scattering, especially for thicker specimens, and this makes the backgroundsubtracted edge signal a non-linear function of thickness, which leads to reconstruction artifacts.…”

Three dimensional mapping of Fe dopants in ceria nanocrystals using direct spectroscopic electron tomography

“…This problem can be overcome by using spectroscopic techniques such as energy dispersive X-ray imaging (EDX) or electron energy loss spectroscopy (EELS). In the past, electron tomography in combination with EELS imaging techniques was applied to investigate nanostructures in both materials science and biology [3][4][5][6][7][8]. In most studies, 2D elemental maps of the object are first calculated at each tilt angle and used as an input for tomographic reconstruction.…”