DIGIPHASE · Development of Maximum Efficiency Phase Contrast Electron Microscopy
Horizon 2020 — Marie Skłodowska-Curie Actions
- Duration
- 2015-07-01 → 2017-06-30
- EU contribution
- €166,157
- Participants
- 1
- Scheme
- MSCA-IF
Lines connect the coordinator with its partners.
Results in brief
Development of Maximum Efficiency Phase Contrast Electron Microscopy
Microscopy has helped enhance our understanding in many fields of science, advancing societies capabilities from technology to medicine. The goal of this project was to investigate new techniques in electron microscopy and employ microscopy to study novel materials. Many materials can handle only limited doses before being significantly altered or destroyed, and in such cases the practical resolving power of the microscope can depend as much on the signal to noise obtained before the sample is damaged as on the imaging optics. This project investigated the use of ptychography to extract information as efficiently as possible. In ptychography a pixelated detector is used to record the details of the electron scattering at low angles, where most of the transmitted electrons can be found, in a scanning transmission electron microscope (STEM). At every probe position an image of this scattering is recorded, creating a four-dimensional dataset. This dataset is then processed digitally to determine the phase and amplitude of the spatial frequencies transmitted by the specimen. It is then possible to construct a phase contrast image by interfering all frequencies and transforming back to real space. Such ptychographic phase contrast imaging was first used to overcome the limitation of spherical aberrations in the electron optics before the advent of aberration correction in hardware. This was achieved by using a small portion of the signal in Fourier space where the aberrations in the interfering disks cancels out. Now however aberration correctors are available that allow atomic resolution at relatively low accelerating voltages. Therefore it is possible to rely on the hardware aberration correction and make use of as much of the signal as possible in Fourier space.
Data: CORDIS, © European Union
Project objective
Electron microscopy is a key technique for imaging and analysis of materials. Although aberration correction has made atomic resolution possible at low accelerating voltages, beam damage remains a critical limitation for many types of materials. The imaging modes currently in use today are inefficient in terms of the number of transmitted electrons detected and the way in which these are used to derive information. Current detectors integrate over details in the angular distribution of scattered intensities, and make use of only a limited range of scattering angles. In the case of scanning transmission electron microscopy (STEM), a wealth of information is contained in the distribution of electron scattering as a function of the illuminating probe position. The proposed work will make use of pixelated detectors to record this four-dimensional data set and develop methods to intelligently utilize the information it contains. This research project has become possible through recent advances in the sensitivity and speed of pixelated detectors, and offers a new path to maximize the information gained per fast electron. Maximum efficiency phase contrast imaging in STEM recovers the full amplitude and phase components of the specimen, with minimum dose, and maximum signal to noise ratio, and maximum contrast that does not require aberrations. In materials science for example it will enable imaging of charge transfer at point defects and interfaces while simultaneous Z-contrast imaging provides interpretability and chemical sensitivity. Similarly, such high sensitivity phase detection will allow the direct imaging of local electric and magnetic fields at the highest possible spatial resolutions, providing many new opportunities for understanding electronic, spintronic and magnetic materials at the heart of today’s technological advances. In biology, maximum efficiency phase contrast imaging may open the door to the ultimate low dose molecular- and bio-imaging.
Original text from CORDIS.
Participants
- UNIVERSITAT WIEN · WienCoordinatorAustria
Links
Data: CORDIS, © European Union