UNT Research, Volume 16, 2006 Page: 30
46 p. : col. ill. ; 28 cm.View a full description of this periodical.
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"With the HRTEM, we can see individual columns of
atoms," explains Gorman. "It gives us images of where the atoms
are sitting, what the structure looks like and, if it's made of layers,
how big the layers are."
The FIB/SEM, also made by FEI, combines a dual-column
focused ion beam and a scanning electron microscope. The SEM
measures surface topography with resolutions of a nanometer by
bringing electrons down to the sample and enabling the user to see
what "reflects" off the sample. The FIB images with gallium ions,
which can also cut open a large structure to help explain undesirable
results. The FIB is also capable of "machining" or cutting into the
surface of a sample. Gorman demonstrates the FIB's ability by show-
ing how he milled the UNT logo onto the surface of a silicon wafer.
"Ten of these logos would fit across the diameter of one of
your hairs," he says.
Each of the instruments has its own capabilities and limita-
tions, Gorman says. For instance, while all three are capable of res-
olutions at the "nano" level, only the LEAP and the HRTEM can
do atomic-scale imaging. The FIB and the HRTEM can also work
at the "micro" (one-millionth of a meter) level, but the HRTEM
is lacking low-level chemistry information. The combination of the
instruments overcomes the limitations of each, says Gorman.DO rPLARn -.kLR, ANulD F UMi<A B_ i, ,'
Of course, the ability to etch the UNT logo onto a surface
seven-millionths of a meter wide doesn't justify the purchase of
these instruments. Rather, it's their promise in research outside
of the strictly microscopic realm that excites Gorman and his
colleagues and graduate students.
A small sampling of the areas in which they are conducting
research includes photovoltaics, fuel cells, computer chips and even
medicine.
Photovoltaics, also known as solar cells, convert sunlight
into electricity. Given the desire to lessen our dependence on
nonrenewable and polluting energy sources such as oil and coal,
researchers are naturally attracted to this renewable and clean
source of energy.
"Most solar cells are grown as big single crystals such as
silicon wafers," Gorman explains. "But we are working in collabo-
ration with researchers at the National Renewable Energy Lab with
polycrystalline structures made of copper, indium and selenium.
The boundaries between the crystals have been shown to be very
conductive, which is a good thing. We can use the FIB to pull out
a boundary and look at it to see why it conducts better. That's
something nobody else in the world is trying.30 )oo6 UNr RESEARCH
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University of North Texas. UNT Research, Volume 16, 2006, periodical, 2006; Denton, Texas. (https://digital.library.unt.edu/ark:/67531/metadc29777/m1/30/?rotate=90: accessed April 24, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting University Relations, Communications & Marketing department for UNT.