TEAM meets 0.5Å
milestone
Performance tests on the TEAM
0.5 microscope have demonstrated 0.5Å information transfer
in both broad beam (TEM) and scanning probe (STEM) operating
modes. Following a battery of acceptance checks at the factory
site in Eindhoven in the fall of 2007, the machine was installed
at the National Center for Electron Microscopy, where it has
taken its place in a specially-designed lab inside one of NCEM's
landmark silos. After extensive further testing and tuning, the
instrument will become available as a user facility in the fall
of 2008.
Test results obtained in the performance trials are shown
in the images below. In the TEM mode (Transmission Electron Microscopy),
a broad beam of electrons is transmitted through the sample and
imaged by an aberration-corrected objective lens. Performance
in this imaging mode is measured from “Young’s fringes” in
a Fourier analysis. The Young’s fringes indicate the extent
of information transfer - the better the microscope, the farther
out from the center of the Fourier image the fringes will extend.
For TEAM 0.5, the fringes clearly extend beyond 0.5Å, marked
by a red circle.
In the STEM mode (Scanning Transmission
Electron Microscopy), an extremely fine, aberration corrected
probe is rastered across the sample and an image is constructed
from the scattered electrons collected by an annular detector.
These results mark a record in
electron microscopy and pave the way for new kinds of experiments
and exploration of the atomic structure in nanomaterials.
The TEAM
Stage
A critical component of electron microscopes is the sample stage. Its mechanical stability limits the resolution and determines the sensitivity to acoustic noise, ground vibrations or temperature changes. A standard stage is as sophisticated as a Swiss watch and as noise-sensitive as a high-powered microphone. The TEAM stage uses a radically new design borrowed from atomic force microscopy. It has only three moving parts and uses much smaller, stiffer components than a conventional stage. As a result, it is extremely stable and unaffected by environmental influences.
The improvement in performance can be seen in a real-time movie showing small gold particles at a magnification of 5 million times while playing loud rock music. The TEAM stage remains stable while the conventional stage "rocks" with the music, making atomic resolution impossible. Research-level high resolution imaging requires much greater stability than that shown in the movie, but the enormous improvement in mechanical stability of the stage is clearly apparent even at this level of resolution. Click on the movie link below to see a demonstration of the TEAM stage performance (left) as compared to a conventional stage (right).
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The microscope is a very special design that starts with the advanced
commercial column produced by FEI company, but adds a number of
unique components, including a specially-developed monochromated
high-brightness gun, a unique new probe corrector designed by CEOS
company and numerous techniques for measurement and alignment developed
by the TEAM partner labs. TEAM 0.5 corrects for spherical aberration,
while the next phase (called TEAM I) will be the world's first
electron microscope to correct for both spherical and chromatic
aberration. TEAM I, which will arrive at NCEM in 2009, will also
feature an ultrastable new stage, designed by the TEAM partners,
that utilizes the technology developed for atomic force microscopy.
