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Upgraded SEM System by Anderson Materials Evaluation, Inc. .pdf



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Upgraded SEM/EDX System
by Anderson Materials Evaluation, Inc.

We recently replaced our Topcon SM-300 SEM/EDX system with a
Topcon ABT-32 SEM/EDX system with an Evex EDX and imaging
computer program. Our present system is shown below:

We have realized a number of improvements as a result. Among these
are:
Image digitization at 256 x 256, 512 x 512, 1024 x 1024, 2048 x 2048,
4096 x 4096, and 8192 x 8192 pixels. The old system only digitized
SEM secondary electron (SED) and backscatter (BSD) images at 1024 x
1024 pixels. Most of our SED and BSD images will now be taken at
higher pixel resolution, while 512 x 512 is often the best resolution for
EDX elemental mapping, since the x-ray emission volume beneath the
surface is much larger than the surface beam entrance cross
section. EDX samples about 1 to 2 micrometers deep into a sample
and the emission volume is about 1 micrometer wide, so the
resolution is much lower in EDX mode than in SED mode.
• We can now map up to 8 elements at one time in the EDX mapping
mode, or while making line scans. We were previously only able to
perform the mapping of one element at time. This greatly reduces the
time it takes to produce a map of several elements. We can now easily
color code each characteristic x-ray emission map and combine them
in various ways, including as superpositions on a SED surface
topography image.

• The EDX energy dispersive detector is on the same side of the
chamber that the secondary electron detector is on, which means
both modes image the sample optimally without having to rotate the
sample with respect to the incoming electron beam as we had to do
on the SM-300 system. Electron beam shadowing effects are now
similar in both the SED and EDX images.
• The EDX x-ray count rates are slightly higher with the new detector,
especially at the lower mass element end of the spectrum. We are
getting a slightly higher energy resolution also with this detector.
• The new Robinson Back Scatter detector has a slightly higher count
rate than our previous detector did. The back-scatter detector allows
one to see higher mass element concentration areas as slightly
brighter than lower mass elements. Because one is only detecting
high energy electrons from the sample, the volume emitting the
signal is substantially deeper into the sample than in a SED
image. The resolution is somewhat less in the BSD mode than in the
SED mode due to sub-surface spreading of the electron beam before
many of the high energy electrons are back-scattered.

• SED images can generally be made at higher resolution than on the
SM-300 system. The resolution specification is 5 nm. The SM-300
had a specification of 4 nm, but this was impractical because
achieving that resolution required such small apertures in the
electron beam column that they quickly became dirty with carbon
accumulations. For practical use, we therefore had to replace the
really small apertures with larger apertures and our resolution was
degraded to about 7 nm. The ABT-32 system is based on a very
different aperture geometry which allows larger apertures placed
differently. Practical operation at up to 40,000 times magnification
is now reasonable.
• All the data is acquired with one computer now, rather than one for
SED and BSD images and another for EDX analysis. Export of data
and images into reports is also more easily accomplished now.
• The sample chamber is slightly larger now than it was in the SM300, though that was also a large chamber.

• We have a wider variety of sample holders and clamps.
• The belt sample manipulation controls are tighter on this
system. Those on the SM-300 had more hysteresis than one would like.
Dr. Lorrie A. Krebs and Dr. Kevin A. Wepasnick are the primary
SEM/EDX users and both of them are very much enjoying using the
improved system. Please feel free to talk to them directly about any
SEM/EDX analysis projects you may have.

Contact Us:
Anderson Materials Evaluation, Inc.
9051 Red Branch Road, Suite C, Columbia, MD 21045
Ph: (410) 740-8562
Toll Free: (866) 350-8882
Fax: (410) 740-8201
Email: contactus@andersonmaterials.com


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