UPDATE
Taking A Closer Look
Tech's electron microscope facility benefits research in nanotechnology, new materials and microelectronics.
By John Toon
IN A DARK, FIRST-FLOOR ROOM at Georgia Tech's School of Materials Science and Engineering, Dr. Z.L. Wang carefully adjusts the controls of a JEOL 4000EX transmission electron microscope. A black-and-white image appears on the monitor to his right, revealing a jumbled pattern of ridges and valleys that covers the surface of a tiny carbon nanosphere barely a quarter of a micron in diameter. The features are just 34 millionths of a meter — 0.34 nanometers — across.
photo by Stanley Leary
Equipment in the Electron Microscope
Facility, used here by Dr. Z.L. Wang, will benefit research in nanotechnology,
novel materials and structures, micro-electronics, new crystals, improved lubricants
and living tissues.
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This glimpse of the sphere's surface shows researchers that they are on the right track in their efforts to turn the tiny graphite balls into efficient solid lubricants for micromachines. It also gives them clues to the next series of experimental steps they should try.
Research into promising areas of nanotechnology, novel materials and structures, ever smaller microelectronics, new crystals, improved lubricants — and even living tissues — demands the use of electron microscopes able to see features a few hundred atoms in size. To make these costly tools available to researchers from many different disciplines, the Georgia Institute of Technology has formed the Electron Microscopy Facility.
The facility's three transmission electron microscopes and single scanning electron microscope have helped examine the molecular arrangement of gold nanocrystals, the charge distribution on a new type of P/N junction used in microelectronics, the growth processes in experimental quantum-dot semiconductors, lubricant layers for high-density disk drives and the configuration of a new phosphor material for computer displays.
In addition to showing the structure of materials on a very small scale, the equipment can also provide data on the chemical composition of these small objects, map electrical charges and measure magnetic domain.
"We want to play an important role in many research programs going on across Georgia Tech, and to promote projects across schools and across other divisions of campus," explains Wang, who is director of the Electron Microscope Facility and an associate professor in the School of Materials Science and Engineering. "We believe that a facility like this is essential to many exciting areas of research."
Wang sees the facility as a key part of a research process that begins with theory and simulation, proceeds to experimental fabrication, then relies on microscopy for feedback on the results. Rather than simply providing a microscopy service, he wants to help researchers design their projects to gain maximum benefit of the facility's equipment, which also includes sample preparation and digital image analysis equipment.
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The cost of developing the Electron Microscopy Facility has been borne by the National Science Foundation, the State of Georgia through the Georgia Research Alliance, and Georgia Tech.
"We want to see this facility grow into one of the major microscopy facilities in the nation," Wang says. "This equipment is essential to many key areas of research, and most of the country's largest and best universities now have it."
The equipment includes:
Hitachi HF-2000 Field
Emission Gun (FEG) Transmission Electron Microscope:
This instrument can perform high spatial-resolution chemical microanalysis,
high-resolution lattice imaging, and high-coherent beam holographic imaging. It
is equipped with a thin window energy dispersive X-ray spectrometer (EDS), which
detects not only heavier elements, but also elements as light as carbon. It also
has a Gatan parallel-detection electron energy-loss spectrometer, which can be
used for quantitative chemical microanalysis of light elements as well as for
studying atomic bonding in solid materials. A 180-degree rotational
electrostatic biprism suitable for electron holography completes the package.
"The brightness of the highly coherent energy source of the Hitachi HF- 2000 allows high resolution lattice imaging at a point-to-point resolution better than 2.3 Angstroms, lattice resolution of one Angstrom, and chemical microanalysis at a spatial resolution of better than 20 Angstroms," Wang notes. "This is an ideal instrument for performing studies of nanostructured materials and interfaces in thin film and composite materials."
The holographic imaging is the only technique that can provide electron phase information, and is therefore suitable for quantitative mapping of electrostatic fields and magnetic fields in materials such as ferroelectric and magnetic recording materials.
To allow in-situ observation of structural evolution, specimens can be cooled to a temperature as low as -160 Celsius using a liquid nitrogen specimen holder, or heated to a temperature of up to 1,300 Celsius using a heated holder. "This capability is vitally important to predicting the lifetime and reliability of advanced materials," Wang notes.
Hitachi S800 Field Emission Gun
Scanning Electron Microscope: This equipment can image materials
at a resolution of better than 30 Angstroms, and perform chemical
microanalysis from bulk specimens.
JEOL 4000EX High Resolution Transmission
Electron Microscope: This device routinely provides point-to-point image
resolution of 1.8 Angstroms and is best suited for recording
high-resolution images of thin foil specimens.
JEOL 100CX II Transmission Electron
Microscope: This instrument is primarily used for undergraduate and
graduate education, though it also has conventional research uses.
Further information is available from Dr. Z.L Wang, School of Materials
Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332-
0245.
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Last updated: Dec. 3, 1997