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Date: 18 September 2014
TEAM 0.5, the World's Most Powerful Transmission Electron Microscope has been Installed at NCEM  


Topic Name: TEAM 0.5, the World's Most Powerful Transmission Electron Microscope has been Installed at NCEM
Category: Optical imaging
    
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Research persons: Uli Dahmen

Location: National Center for Electron Microscopy, Department of Energy, United States

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TEAM 0.5, the World's Most Powerful Transmission Electron Microscope has been Installed at NCEM

TEAM 0.5, the world's most powerful transmission electron microscope —
capable of producing images with half-angstrom resolution (half a ten-billionth
of a meter), less than the diameter of a single hydrogen
atom
— has been installed at the Department
of Energy
's National Center
for Electron Microscopy
(NCEM) at Lawrence
Berkeley National Laboratory
.
"We have beam down the column," announced Uli Dahmen of Berkeley
Lab's Materials Sciences Division, who is head of NCEM and director of DOE's
collaborative TEAM Project, when the TEAM 0.5 microscope first delivered its
ultrabright electron beam at Berkeley Lab in late December.
The TEAM Project (TEAM stands for Transmission Electron Aberration-corrected
Microscope) is led by Berkeley Lab in a collaboration with DOE's
Argonne
and Oak Ridge
National Laboratories
, the Frederick
Seitz Materials Laboratory of the University of Illinois
, and two private
companies specializing in electron microscopy, the FEI Company headquartered in
Portland, Oregon, and CEOS of
Heidelberg, Germany
.
Now that TEAM 0.5's basic systems are operational, additional components and
facilities are being completed and tuned, including a state-of-the-art control
room display that shows the sample under the microscope on a flat panel
resembling a wide-screen, high-definition TV. After a long series of rigorous
tests and adjustments, TEAM 0.5 will become available to outside users by
October, 2008.

Atom by atom in 3-D


In preliminary tests at the FEI Company, before the TEAM 0.5 was shipped,
NCEM's Christian Kisielowski tested the microscope's ability to resolve
individual atoms and precisely locate their positions in three dimensions. He
made a series of images of two gold crystals connected by a "nanobridge"
only a few dozen atoms wide. From each exposure to the next, individual gold
atoms could be seen changing positions.
To achieve this extraordinary resolution, TEAM 0.5 embodies technical
advances that have only recently become possible, including ultra-stable
electronics, improved aberration correctors, and an extremely bright electron
source.
Spherical aberration degrades images, making points of light look like disks,
and correcting it can make dramatic improvements to image resolution. (This was
famously demonstrated in 1993, when spherical aberration in the Hubble Space
Telescope's optical lenses was corrected in a special space mission.) In the
case of electron microscopes, a series of multipole magnetic lenses of varying
geometries shapes the electron beam.
"Correcting spherical aberration in an electron microscope has long been
possible in theory," says Dahmen. "But only recently has it become
practical, because today's stable electronics reduce drift and fast computers
allow continuous adjustments in real time." Corrector technology has even
become available commercially, says Dahmen, "but no off-the-shelf corrector
can match TEAM 0.5's ability to compensate even higher-order aberrations."
Correcting spherical aberration makes it possible to use the TEAM 0.5 not
only for broad-beam, "wide-angle" images but also for scanning
transmission electron microscopy (STEM), in which the tightly focused electron
beam is moved across the sample as a probe, capable of performing spectroscopy
on one atom at a time — an ideal way to precisely locate impurities in an
otherwise homogeneous sample, such as individual dopant atoms in a semiconductor
material.
Aberration correction is also essential for another advanced feature of TEAM
0.5: its ability to maintain high resolution with lower electron beam energies.
"Low energy electrons have longer wavelengths, so they are harder to
focus," Dahmen explains. "Aberration correction allows better than
one-angstrom resolution with excellent contrast even at 80 kilovolts. This is
important when you don't want to damage the sample with a high-energy beam —
in biological studies, for example."
It's not just high resolution that makes TEAM 0.5 the world's best
microscope, Dahmen says. When all the electrons in the beam focus at the same
plane, image contrast and signal-to-noise ratio improve tremendously.
"It's because the signal-to-noise ratio is so good that you can adjust
focus atom by atom, with enough sensitivity to obtain information about the
three-dimensional atomic structure of a single nanoparticle." Dahmen adds,
"This brings us within reach of meeting the great challenge posed by the
famous physicist Richard Feynman in 1959: the ability to analyze any chemical
substance simply by looking to see where the atoms are."
The position of individual atoms in a structure can be determined by taking
images at different angles, from which the computer reconstructs a 3-D tomograph
of the sample, as in a CAT scan. To make this possible an innovative system
capable of tilting and rotating the sample, and moving it up, down, or sideways
under the electron beam, is also being developed at NCEM.
Much smaller than sample stages now in use, the new TEAM stage will be housed
entirely inside the microscope column. Manipulating the sample by such methods
as minute piezoelectric "crawlers" that change shape when electricity
is applied, the new stage will be able to control and reproduce the sample's
position and attitude with an accuracy of less than a billionth of a meter.
Installation of the new stage must await the next phase of the TEAM Project:
the TEAM I microscope, due to be set up at NCEM early in 2009.
While TEAM 0.5 corrects spherical aberration in both the "probe"
beam (the electron beam before it strikes the sample) and the image beam (after
it exits the sample, but before it reaches the detector), TEAM I will also
correct chromatic aberration in the image beam, which has never beeen
accomplished before. Spherical aberration is caused by the shape of a lens;
chromatic aberration results when a lens refracts light or electrons of
different wavelengths (different colors or energies) at different angles.
"Correcting chromatic aberration is harder and takes more space,"
says Dahmen. "The chromatic aberration corrector will add two feet to the
height of the TEAM I column. But the new configuration will also allow us to
enlarge the gap between the pole pieces, into which the sample fits. In TEAM 0.5
this gap is only about two millimeters, so we have to use traditional
outside-mounted sample stages, with limited space to manipulate the sample. In
TEAM I the gap will be five millimeters; the sample stage will have much greater
freedom of movement."

New vistas in the realm of the small


TEAM 0.5 and TEAM I will be housed side by side at NCEM for some time,
occupying the two multistory "silos" that until recently were the
homes of the historic High-Voltage Electron Microscope and the Atomic Resolution
Microscope, the most powerful microscopes in the world when NCEM was established
in the early 1980s.
Ambitious as those microscopes were in their day, says TEAM's Project
Manager, Peter Denes of the Engineering Division, "when the TEAM Project
was launched in 2004, it was not quite clear if the goals could even be
achieved. The electron microscopy community had never done a collaborative
project like TEAM before, and certainly not with full DOE project-management
rigor."
Says Denes, "Perhaps the biggest contributor to success was a series of
scientific workshops that contributed to forming a converging opinion on what
the next steps would be, and what would constitute success. That helped in
getting everyone — if not quite on the same page — at least in the same
book."
Dahmen agrees. "This is a big jump for the microscopy community. TEAM's
success will open the door to other ambitious developments around the
world."
Dahmen suggests at least two broad categories of researchers who will benefit
from the powerful new electron microscopes: experts with sophisticated
microscopy problems to solve, and scientists less familiar with electron
microscopy but with a particular problem for which microscopy can provide the
answer.
"For example, Jim Zuo at the University of Illinois is doing studies of
electron diffraction from the surface of single nanoparticles," Dahmen
says. "He sees evidence of surface contraction. But when we at NCEM do
imaging of similar nanoparticles, we find that the surface is expanding. Jim
looks forward to using the TEAM microscope because it can do diffraction and
imaging of the same particle at the same time — a grand experiment, and the
only way to solve the apparent contradiction."
An example of a problem-solving nonspecialist, says Dahmen, might be a
materials scientist who has created a new kind of nanostructure, such as a
tetrapod semiconductor, and needs to know exactly where in this complex,
three-dimensional shape the impurity atoms reside. "TEAM's ability to image
the structure in 3-D through tomography and its ability to do spectroscopy with
single-atom sensitivity can identify each kind of atom at each position in the
structure. That has never been possible before."
The basic TEAM components of aberration correction, enhanced signal-to-noise
ratio, single-atom sensitivity, and an ultrabright beam that can be used in both
TEM and STEM modes — all the while manipulating the sample in the beam — are
goals that until recently seemed at the very edge of technological daring. All
are on track, and some have been solved ahead of schedule. The TEAM Project's
continuing success, signaled by the installation of TEAM 0.5 at NCEM, has opened
the possibility of numerous future advances in electron microscopy that were
barely conceivable when TEAM was launched.
Note for High-Definition Television
High-definition television (HDTV) is a digital television broadcasting system with greater resolution than traditional television systems (NTSC, SECAM, PAL). HDTV is digitally broadcast because digital television (DTV) requires less bandwidth if sufficient video compression is used. HDTV technology was introduced in the United States in the 1990s by the Digital HDTV Grand Alliance, a group of television companies.
HDTV broadcast systems are defined threefold, by:
The number of lines in the vertical display resolution. 
The scanning system: progressive scanning (p) or interlaced scanning (i). Progressive scanning redraws an image frame (all of its lines) when refreshing each image. Interlaced scanning redraws the image field (every second line) per each image refresh operation, and then redraws the remaining lines during a second refreshing. Interlaced scanning yields greater image resolution if subject is not moving, but loses up to half of the resolution and suffers "combing" artifacts when subject is moving. 
The number of frames per second or fields per second.
Note for Scanning Transmission Electron Microscope
A scanning transmission electron microscope (STEM) is a type of transmission electron microscope. With it, the electrons pass through the specimen, but, as in scanning electron microscopy, the electron optics focus the beam into a narrow spot which is scanned over the sample in a raster.
The rastering of the beam across the sample makes these microscopes suitable for analysis techniques such as mapping by energy dispersive X-ray (EDX) spectroscopy, electron energy loss spectroscopy (EELS) and annular dark-field imaging (ADF). These signals can be obtained simultaneously, allowing direct correlation of image and quantitative data.
By using a STEM and a high-angle detector, it is possible to form atomic resolution images where the contrast is directly related to the atomic number. This is in contrast to the conventional high resolution electron microscopy technique, which uses phase-contrast, and therefore produces results which need interpretation by simulation.
The first STEM was built in 1938 by Baron Manfred von Ardenne, working in Berlin for Siemens. However, the results were inferior to that of TEM at the time, and von Ardenne only spent two years working on the problem. The microscope was destroyed in an air raid in 1944, and von Ardenne did not return to the field after WWII.
About  Hubble Space Telescope
The Hubble Space Telescope (HST) is a telescope in orbit around the Earth, named after astronomer Edwin Hubble. Its position outside the Earth's atmosphere provides significant advantages over ground-based telescopes — images are not blurred by the atmosphere, there is no background from light scattered by the air, and the Hubble can observe ultra-violet light that is normally absorbed by the ozone layer in observations made from Earth. Though not the first space telescope, since its launch in 1990, it has become one of the most important instruments in the history of astronomy. With it, astronomers have made many observations leading to breakthroughs in astrophysics. Hubble's Ultra Deep Field has the most detailed visible light image of the most distant objects ever taken.
The construction and launch of the Hubble was beset by delays and budget problems. Then, soon after its 1990 launch, it was found that the main mirror suffered from spherical aberration due to faulty quality control during its manufacturing, severely compromising the telescope's capabilities. However, after a servicing mission in 1993, the telescope was restored to its intended quality and became a vital research tool as well as a public relations boon for astronomy. The HST is part of NASA's Great Observatories series, with the Compton Gamma Ray Observatory, the Chandra X-ray Observatory, and the Spitzer Space
Telescope. Hubble is a collaboration between NASA and the European Space Agency.
The multi-institutional TEAM project represents a new kind of distributed
planning and cooperation for the electron microscope community, moving beyond
the limited, incremental improvements of individual investigators and harnessing
the power of collaboration. Argonne National Laboratory is leading the
development of the chromatic-aberration corrector in close collaboration with
CEOS in Heidelberg. The University of Illinois's Frederick Seitz Materials
Laboratory is jointly developing the new piezoelectric-controlled sample stage
with Berkeley Lab's NCEM, and Oak Ridge National Laboratory is helping to
optimize the new probe corrector. NCEM acts as project leader to integrate the
individual components into single instruments, in close collaboration with all
other TEAM partners. The TEAM Project is supported by the U.S. Department of
Energy's Office of Science.
In figure 1, Where these two gold crystals meet they are joined by a complex
arrangement of atoms, forming a nanobridge that accommodates their different
orientations. The gold atoms are 2.3 angstroms apart. TEAM 0.5's unprecedented
signal-to-noise ratio makes it possible to distinguish individual atoms and, at
the edges of the two crystals, deduce their position in three dimensions.
In figure 2, After launch, the Hubble Space Telescope was found to suffer
from spherical aberration (left). Astronauts corrected the problem and image
quality improved markedly. TEAM 0.5 is the first electron microscope capable of
correcting higher-order spherical aberration.
In figure 3, TEAM 0.5, the world's best transmission electron microscope, is
being assembled at the National Center for Electron Microscopy. (Photo Roy
Kaltschmidt, Berkeley Lab CSO)


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