Events

Coming Colloquium

 

HONG KONG BAPTIST UNIVERSITY
Department of Physics &
Institute of Advanced Materials

 

JOINT COLLOQUIUM

 

From Low Dose Electron Microscopy Toward No Dose Electron Microscopy: Revealing the Dynamics of Single Molecule at High Space/ Time Resolution

 

Speaker:
Prof. Furong CHEN
Dept. of Materials Science and Engineering,
City University, Kowloon, Hong Kong

 

Date: March 23, 2018 (Friday)
Time: 2:30pm – 3:30pm
Venue: SCT909, Science Tower, HSH Campus


Abstract
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The ultimate goal for materials scientists is to understand the functions and to control the properties of materials. Richard Feynman gave the implication that the “atom” in 3D is the best alphabet for this purpose. The simplest example is the band-gap energy and mechanical energy of the so-called 2D material graphene can be modified due to the existence of intrinsic rippling and of externally applied strain deviates the atoms in graphene sheet into 3D. The mechanical and electronic properties of graphene are therefore encoded in the 3D positions of atom. Another way to deduce the physical properties of nano-object is to look at the dynamics with high time resolution. In my talk, I will first demonstrate the low dose electron holography can be first reconstructed from a focal series of low voltage and low dose high resolution images.. And then I show how the 3D atomic resolution tomogram can be reconstructed from a hologram. The reconstructed atomic resolution tomogram of nano-bridge Au, wedge Ge and the nano-cube MgO will be shown. Futhermore , I show the result of electron beam induced dynamics of MoS2 at atomic resolution but with a time resolution of a few ten seconds. Although the beam dose rate is already reduced to 25e/Å2 sec, loss of edge Mo and S atoms is clearly evident. The experimental example of single molecular imaging for Oleic acid molecules also shows that even with the dose rate of 5e/Å.sec., we still see the segments of the Oleic molecule, i.e. electron beam / sample interaction still play a dominant role so that visualization of 3D molecular network is hindered.

Finally, I show the our instrumentation development of a low voltage/ environmental table top electron microscope toward “no dose” interaction free “quantum electron microscope”. This microscope is a compact system integrated with self-designed aberration corrected electron optics with the key elements of beam splitter and Zeno quantum resonantor. The final remarks will end with a development is also migrating toward to link with ultrafast electron microscopy for the dynamics of the soft materials at high spatial/ time resolution without damage of the soft materials.





All Interested Are Welcome!
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