Heide Ibrahim

Heide Ibrahim
Tel.: +1 (514) 228-6865
Fax: +1 (450) 929-8102

Looking closer and closer into the details of nature is the aim and motivation of natural sciences. Starting with optical microscopy one had the chance to observe with much higher resolution than the bare human eye. Electron microscopy extended this to levels below the angstrom scale, making atoms visible. Resolving faster and faster events is the other mainspring of scientific development and since the invention of lasers the femtosecond (10e-15s, fs) and even attosecond (10e-18s, as) regimes have been accessed. These spectroscopic approaches have provided observations of molecular vibrations, including their manipulation, electron movements, and molecular orbitals. However, microscopic real–space imaging with atomic (or near atomic) resolution is not possible with these techniques. X-ray and electron diffraction can combine high spatial and temporal resolution but deliver this information in the ‘reciprocal space’ of atomic positions, and so loose information on local spatial events like defect dynamics, rapid nucleation and growth of isolated crystallites, shock wave propagation etc. For time-resolved, real-space investigation of irreversible processes like these a new powerful tool is required; a Dynamic Transmission Electron Microscope (DTEM).
The irreversible nature of the observed processes prevents us from ‘cycling’ (or averaging) over thousands of shots. We must be able to acquire TEM images with a “single – shot”, which requires at least 10e8 electrons in each nanosecond exposure. Therefore, the conventional thermionic emission source on our existing TEM will be replaced with a photoemission source that will be driven by a laser.
In a typical DTEM pump-probe experiment a nanosecond (10e-9 s, ns) laser pulse photo–initiates structural transformation in the sample and after a variable time delay a nanosecond TEM exposure generates a ‘snapshot’ image of the specimen. A wide range of applications ranging from semi-conductor industries to medicine is interested in such a single shot instrument.