Facility Feature: Hitachi STEM
by Yimei Zhu
Yimei Zhu
The new Hitachi scanning transmission electron microscope (STEM) in the CFN is an amazing visualization tool for exploring the nanoworld. With it, we can see how atoms are structured and behave in nanomaterials.
The microscope can magnify an atom up to 50 million times. To get a feel for that power, think about blowing up a ping-pong ball to the size of the moon!
The instrument is the first aberration-corrected, high-resolution electron microscope manufactured by Hitachi and the only one of its kind in the United States. In the microscope, electrons emitted from a cold-field source are accelerated to 200 thousand electron volts of energy to image atoms in solid sample. Those electrons travel through dozens of electro-magnetic lenses in a complex optical setting that can reach a spatial resolution of below 1 angstrom. (Usually, the bond length in a solid is around 0.3-0.4 nanometers).
The Hitachi is also equipped with a high-resolution, energy-loss spectrometer. It allows us to take images and spectra at the same time. In other words, we can visualize not only the structural arrangement of atoms, but also identify their chemical nature and electronic bonding states, including ionicity and charge transfer, all at atomic resolution.
This state-of-the-art instrument is housed in a high-precision laboratory designed with a novel “room-in-room” concept. The lab has very strict controls for temperature (22°±0.03°C/day), acoustic vibration (< 0.75 um/sec) and magnetic field (<0.01 mGauss).
The instrument has been in full operation since the fall of 2007, and we have been accepting users for various projects, including those on energy-related materials research (see Jia Wang’s piece).
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