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Batson Nano-Scale Discovery Collaboration

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Scanning Transmisson Electron Microscopy

P.E. Batson and M.J. Lagos

We can now make an electron beam that is about the size of a hydrogen atom, and can actually place that beam on or between atoms within materials to examine how they are put together, how they might function in a device, how they might be used to measure biological activity, or hasten a chemical reaction.  The image above shows the positions of columns of atoms in an interface between two metal oxide structures.We also can perform very simple experiments to understand how materials, in general, act at very short times.  Atoms and molecules move about and vibrate at very high speeds.  We can now, for the first time, visualize the behavior of very small structures at atto-second time scales in an electron microscope, and plan experiments to test these ideas. The film clip at the upper right is a calculation of the forces acting on a 2 nm-sized gold sphere during the passage of a fast electron in the STEM.  These forces change dramatically during a few atto-seconds, inducing changes in the nano-particle that inform us about how such structures might be used for energy-gathering, catalysis and information transfer.  


Much slower behavior, the transport of heat from one part of a specimen to another, can be understood with this instrument as well.  Measuring  energy changes within a specimen to an accuracy of 10 milli-eV, corresponding to pico-second  timescales, allows us to characterize phonon behavior in nano-scale structures. The middle figure shows how the phonon signal in silicon dioxide at 150 meV changes as the electron beam  is moved across a semiconductor sample.        

The new instrument is a Nion UltraSTEM 100 kV STEM with the Hermes  electron monochromater.  We are now operating at 60 kV beam energy and  obtain Angstrom level images with 10 meV beam energy resolution  using about 20 pico-amps of current.  The new  STEM is housed in a room having very low noise intereference -- electrical, magnetic, floor vibration, acoustic, and temperature.  

At Rutgers we are exploring practical materials with new collaborations, but also wondering about “What if …” questions whose ultimate use we can only imagine. 

We acknowledge the financial support of the Department of Energy,  Basic Energy Sciences (DOE project #DE-SC0005132) for work on Electron Beam Induced Forces, and the National Science Foundation MRI #0959905 for the instrumental development.

Atto-Second Forces during the passing of a swift electron.

Atto-Second Forces during the passing of a swift electron.

Phonon Spectra in SiO2 at ~150 meV

 

Nion UltraSTEM at Rutgers

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