报告题目：Addressing Richard Feynman’s Dream : Development of High Space/ Time Resolved Electron Microscopy for Soft Material Movie
报告人：Prof. Fu-Rong Chen (Dept. of Materials Science and Engineering, City University, Kowloon, Hong Kong)
The ultimate goal for materials scientists is to understand the functions and to control the properties of materials. Richard Feynman gave an implication that the “atom” in 3D and its dynamics are the best alphabet for this purpose. Over the past decade, the ability of electron microscopy to acquire atomic-resolution images with single-atom sensitivity has opened up for unprecedented insight into materials structures and dynamics. However, the progress has also shown that observations at the atomic-level require an intense electron illumination that generally alters the samples during observation, especially, for soft materials, e.g., functional molecules and RNA/ DNA etc. Radiolysis causing artifacts and wrong interpretation for chemical reactions in-situ TEM involving with gas and liquid environments are evidenced. The cryo-EM was proposed to slow down electron beam damage during imaging at low temperature, however, there still exists three bottlenecks for cryo-EM:
(1) the shape of sample may change when it is cooled down to low temperature
(2) since the sample is sealed inside an ice layer, molecule dynamics of sample at room temperature gets lost
(3) The contrast of a small (single) molecule is still hindered to be quantitatively reconstructed.
In my talk, I will first show our exercise to control over the electron dose, dose-rate and energy to suppress electron-induced alterations and to enable meaningful atomic resolution dynamics observations for MoS2 nano catalyst and single Oleic acid molecule. To fulfill Feynman’s dream for achieving high spatial/ temporal resolution, an unique time resolved aberration corrected environmental (TRACE) TEM being stetted up in cityU of Hong Kong. This unique aberration corrected TEM has a special femto-second pulse electron gun and a low dose sensitive camera Gatan K3 integrated with a modern fast kicker deflectors under projector lens plus compressive sensing technology that allows the observing molecules to be recorded with a video rate in micro-second range in a very low dose mode without radiation damage. Finally, I show the progress in instrumentation development of a low voltage/ environmental tabletop electron microscope toward quantum seeing in the dark, i.e., an “interaction free electron microscope”. This microscope is a compact system integrated with self-designed aberration corrected electron optics with the key elements of highly coherent pulse source, beam splitter, a Zeno quantum resonator and a fast recording camera.