Research Topics

Advancing TEM Techniques

In conventional TEM experiments, only the intensity of the wave function can be measured. The phase information is lost when the electron is detected by the CCD camera. We are developing a new approach that combines off-axis and in-line holography and allows reliable phase information to be recovered for all spatial frequencies up to a given resolution. For a desired signal-to-noise ratio, the required total exposure time is lower than that for traditional high-resolution off-axis electron holography.

Hybridization of Off-Axis and In-line High-Resolution Electron Holography

In conventional TEM experiments, only the intensity of the wave function can be measured. The phase information is lost when the electron is detected by the CCD camera. We are developing a new approach that combines off-axis and in-line holography and allows reliable phase information to be recovered for all spatial frequencies up to a given resolution. For a desired signal-to-noise ratio, the required total exposure time is lower than that for traditional high-resolution off-axis electron holography. [more]
Valence EELS, where the signal originates majorly from Coulomb interactions between the weakly bound outer-shell electrons and the incident beam, is of great academic interest. With the proper experimental set-up, the dispersion of the electronic excitations, such as guided mode, surface and bulk plasmons, can be directly measured. In this research VEELS in the SESAM will be employed to explore the spatial variation of the bandgap within multilayered structures and the properties of the dispersion within frequency-momentum (ω-q) space will be investigated.

Study of Valence Electron Energy-Loss Spectroscopy

Valence EELS, where the signal originates majorly from Coulomb interactions between the weakly bound outer-shell electrons and the incident beam, is of great academic interest. With the proper experimental set-up, the dispersion of the electronic excitations, such as guided mode, surface and bulk plasmons, can be directly measured. In this research VEELS in the SESAM will be employed to explore the spatial variation of the bandgap within multilayered structures and the properties of the dispersion within frequency-momentum (ω-q) space will be investigated. [more]




Previous Research Topics

Light elements, such as lithium, are difficult to detect using high-angle annular dark-field imaging (HAADF) in STEM because of their weak atomic scattering. Recently, a novel imaging mode in aberration-corrected STEM was presented that uses an annular detector spanning an angular range mainly within the illumination cone of the focused electron beam. It was shown that due to the smaller dependence on atomic number Z, approximately Z1/3 compared to Z2 in HAADF, the resulting images enable one to visualize the light element columns. This imaging mode has been called annular bright-field (ABF) imaging.

Contrast Investigation of Annular Bright-Field Imaging in Scanning Transmission Electron Microscopy of LiFePO4

Light elements, such as lithium, are difficult to detect using high-angle annular dark-field imaging (HAADF) in STEM because of their weak atomic scattering. Recently, a novel imaging mode in aberration-corrected STEM was presented that uses an annular detector spanning an angular range mainly within the illumination cone of the focused electron beam. It was shown that due to the smaller dependence on atomic number Z, approximately Z1/3 compared to Z2 in HAADF, the resulting images enable one to visualize the light element columns. This imaging mode has been called annular bright-field (ABF) imaging. [more]
The development of atomic-scale magnetic characterization techniques promises further progress in nanotechnology-based devices, such as high density data storage. A reliable technique to perform magnetism measurement at such high spatial resolution is based on electron magnetic circular dichroism (EMCD). Recently, an attractive method using an astigmatic electron probe within a Cs-corrected scanning transmission electron microscope (STEM) has been proposed by Jan Rusz et al., theoretically showing great potential for measuring EMCD with atomic resolution. In this project, we aim to obtain the EMCD signal with atomic resolution experimentally.

Resolving Magnetic Properties at Atomic Scale

The development of atomic-scale magnetic characterization techniques promises further progress in nanotechnology-based devices, such as high density data storage. A reliable technique to perform magnetism measurement at such high spatial resolution is based on electron magnetic circular dichroism (EMCD). Recently, an attractive method using an astigmatic electron probe within a Cs-corrected scanning transmission electron microscope (STEM) has been proposed by Jan Rusz et al., theoretically showing great potential for measuring EMCD with atomic resolution. In this project, we aim to obtain the EMCD signal with atomic resolution experimentally. [more]
 
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