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Master thesis: Atomic-scale imaging of electronic materials and devices by transmission electron microscopy and spectroscopy

Advertising institute: ER-C-2 - Materials Science and Technology
Reference number: D032/2018, Physics

The demand for electronic devices with increased functionality, faster speed, and lower energy consumption pushes the drastic reduction in the device size at a rapid pace. For devices and materials with dimensions in the nm regime, atomic scale imaging of the materials is often necessary to gain understandings of the properties of materials and mechanisms of phenomena at atomic level. State-ofthe-art aberration corrected transmission electron microscopy (TEM) techniques are unique in quantification of the atomic structure, chemical composition, and bonding / electronic structure on the atomic scale.

A transmission electron microscope can be operated in a conventional imaging mode using a parallel beam illuminating the sample, or in a probe mode using a sub-angstrom convergent beam scanning across over the sample (STEM). There is a dramatic increase of interest in the aberration corrected STEM technique because it allows complementary signals generated from the beam-specimen interaction to be collected simultaneously, thereby permit us to resolve structural details and to map compositional and bonding information on the atomic scale. In particular, the inelastic scattered electrons, suffering energy loss during the beam-specimen interaction, carry information of the unoccupied electronic states of the materials, which can be characterized by electron energy loss spectroscopy (EELS). For transition metal oxide electronic materials such as SrTiO3, defects and interfaces often modify the local material properties by altering the electronic structures or valence states of the transition metals with respect to the ideal materials. Quantitative atomic scale imaging of local atomic and spectroscopic information of defects and interfaces in electronic materials and devices will be the focus of this thesis.

First, you will be trained to prepare thin TEM specimens with thickness about 30 nm from the materials or devices. Then you will be trained to image the specimens on the aberration-corrected electron microscopes. By combination of the complementary information obtained from different signals, you should be able to determine the atomic structural details of the defects and interfaces, including composition and electronic bonding information, at the atomic level. Your work will address transition metal oxides for resistive switching applications, and will benefit to a comprehensive understanding of properties of the materials and mechanisms of the phenomena at atomic level.

Contact person:
Dr. Hongchu Du
Forschungszentrum Jülich
Ernst Ruska-Centre for Electron microscopy