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Oregon
State University |
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USER INFORMATION AND FACILITY POLICIES |
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Services The
Electron Microscopy Facility provides instrumentation, skills, and
specialized training necessary to analyze microstructure of solid
biological and physical substances.
Instrument
operation and specimen preparation services can be provided.
Clients are encouraged to consult with our staff regarding
experimental design, data requirements, sampling, specimen preparation,
and scheduling before committing experiments to microscopy.
Many clients have laboratory personnel operate instruments but
are present during microscopy sessions.
There is no charge for estimates or consultations.
Results and sample materials not consumed for microscopy are
returned to the client. Priority
is given to budgeted university research although work may be accepted
from other sources. Work is
scheduled as received unless special handling is requested.
Data return time is usually under two weeks. Data produced for clients and information of a proprietary
nature is treated with strict confidentiality. TRANSMISSION
ELECTRON MICROSCOPE SERVICES Transmission
electron microscopy (TEM) and scanning transmission electron microscopy
(STEM) provide means to study details of structure too small to be seen
by conventional compound light microscopy.
High quality light microscopes resolve details larger that 0.2
micrometer to useful magnification as high as 1000x. Our transmission electron microscope resolves to about 0.1
nanometer (nm) with a direct magnification range from 30x to 750,000x.
TEM and STEM supplements, but does not necessarily replace, light
microscopy or other analytical techniques.
For
transmission and scanning transmission EM, an electron beam projected
through the microscope column is focused by magnetic lenses. The beam acquires information by loss of energy and electron
scattering as it passes through the specimen.
Because electron beams have limited ability to penetrate
substances, specimens must be very thin and the instrument column kept
at high vacuum to enhance electron transmission and penetration. Images
and electron diffraction patterns formed by the microscope may be viewed
directly or recorded on photographic film. For
transmission and scanning transmission EM, specimen thinness
requirements restrict applications to studies of tiny particles,
macromolecules, copies (replicas) of surfaces, microtomed sections, and
chemically thinned foils. Techniques
are available to produce suitably thin specimens from most substances.
Transmission microscopy is usually the appropriate method for
microstructure imaging. Scanning
transmission methods are often more appropriate to imaging relating
specimen chemistry with microstructure. Specimen
preparation for TEM/STEM can be exacting, tedious, and time consuming.
Although particulate specimens may often be prepared and ready
for examination within a few minutes, bulk biological tissues or
physical specimens must be subjected to lengthy, involved preparation
procedures which ultimately reduce the samples to less than100
nanometers (nm) in thickness. A
sample for TEM must fit on a specimen support screen 3.0 mm in diameter
and be stable in a high vacuum and under electron beam irradiation. The EM Facility can prepare most specimens for TEM/STEM.
Charges are made for microscope time, technical assistance, film,
and specimen preparation services.
X-ray spectrometry and image analysis services are available with
TEM and STEM microscopy. SCANNING
ELECTRON MICROSCOPY SERVICES Scanning
electron microscopy (SEM) permits study of three dimensional surface
detail of biological and physical specimens at magnifications
approaching100,000 times with spatial resolution approaching 1.5 nm.
In SEM, an electron beam, focused by magnetic lenses, is
projected through an evacuated column and scanned as a fine probe of
electricity across the specimen surface.
Energy from this scanning beam causes the specimen to emit
radiation that is detected and used to image the specimen surface.
Images produced from several types of emitted radiation may be
viewed directly or recorded photographically to yield structural,
chemical and electrical information about the sample being examined. Because
the beam does not pass through the specimen, sample thickness is not a
limitation in SEM; samples several cubic centimeters in volume may be
accommodated. Specimens for
SEM are most aesthetic when they have pronounced three dimensional
topography. Wet samples must be prepared by drying methods which retain
the hydrated appearance of fine structure, and samples that behave as
electrical insulators are usually coated with a conductive metal film
before microscopy. X-ray
spectrometry and image analysis services are available with SEM
microscopy. Charges
are made for instrument time, technical assistance, and specimen
preparation procedures. Combining
electron microscopy with x-ray spectrometric analysis can be an
informative method for more fully characterizing the microstructure and
microchemistry of solid objects. Our
electron microscopes image structure at high magnification with high
spatial resolution. Simultaneously
with the production of an image, a nondestructive x-ray
spectrometric analysis can generate qualitative and quantitative
elemental composition information from the specimen being examined.
The chemical data may be mapped over a structural image to show
distribution of elements with respect to structure, or may be presented
as graphed spectra and tabulated reports. Carbon
and all other elements with atomic numbers greater than 5 (boron) are
detectable by x-ray spectrometry. On
appropriate samples spatial resolution of elemental concentrations may
exceed one micrometer and quantities as low as about 1 x 10-5
gram may be detected to an accuracy of +/-1 weight %. Samples
for TEM/STEM spectrochemical analysis may be in the form of small, dry
particulates or dry bulk substances thinned to flat, thin slices.
Wet samples for SEM/x-ray spectrochemical analysis should
be prepared and dried by methods which retain hydrated appearance and
chemistry of fine structure, and samples that behave as electrical
insulators must be coated with conductive carbon films before
examination. SEM samples
may be up to 100 mm3. Specimens
for SEM are most aesthetic when they have pronounced three dimensional
topography, whereas ideal specimens for quantitative x-ray
spectrochemical analysis are flat and chemically homogeneous, although
rough, heterogeneous substances can be evaluated qualitatively.
The EM facility can assist with the preparation of samples for
TEM/STEM/SEM and energy dispersive x-ray analysis. Charges
are made for microscope time, film, specimen preparation procedures,
and, when appropriate, for technical assistance with qualitative and
quantitative data reduction and analysis reports. Those
interested in x-ray spectrometry should refer to the information
in the section "Guidelines for X-ray Energy Spectrometer" near the
end of this manual. Image
analysis may enhance a study by providing more qualitative or
quantitative descriptions of imaged structural features.
The analysis is accomplished by digitizing an image, modifying
image grey levels, and computing size parameters such as perimeter or
area and shape factors such as the ellipicity of image features. Image digitization, modification, and analysis is done by a
computer which directly accepts images, measures and statistically
evaluates the identified morphological details, and produces a tabulated
report. Image
analysis capabilities are available in the Electron Microscope Facility.
Charges cover film, graphic supplies, and image acquisition, data
reduction, and report assistance. The
Facility's main mission is research support service. Our instructional programs support our research orientation. Demonstration
and lecture services are available in support of institutional
instructional programs. Instructional
accounts are charges for demonstration services.
Guest lecturing requiring less than 2.0 hours staff time is
available at no charge. The
Facility sponsors instructional programs for clients, students and
interested persons wanting information about capabilities and
limitations of equipment, the analyses which can be performed, or
specific specimen preparation or instrument operation techniques.
Instruction
in hands‑on instrument operation and/or specimen preparation
procedures is a routine function of this laboratory but limited to
faculty, staff and students who demonstrate clear, valid need for
training. Instruction is not provided simply because an applicant
believes it would be "nice to know" or "might be useful
someday". Training is
scheduled for small groups. Charges may be made to cover costs of
consumables or staff time. We
provide two options for those wanting to learn about electron
microscopy. BI 466/566 Option:
For those with a general curiosity about
electron microscopy, undertaking research which requires electron
microscopy, or intending to operate electron microscopes, BI 466/566,
offered for 3 credits in Winter term, is an overview lecture and
demonstration course covering:
Instrument
types and development;
Electron
beams, signal production;
Lenses, lens properties;
Vacuum systems;
Specimen preparation;
Image capture and analysis;
Electron diffraction;
Electron energy loss and x-ray spectrometries This
course addresses transmission and scanning electron microscopy applied
to biological, earth sciences, and materials studies and gives enrollees
an ability to understand electron microscopy literature, design and
interpret research using electron microscopy, and better appreciate the
complexities involved in specimen preparation and electron microscope
operation. BOT 505A Option: Persons
with funded research which will be done at OSU who need to do lengthily
"hands-on" electron microscopy projects may receive technical
instruction specific to the types of specimens and microscopy required
by their studies. Training
can be arranged in Summer,
Fall, or Spring
term, and academic credit adjusted to reflect the time and scope of the
training provided. Training
arrangements and consent of the Electron Microscope Facility instructor
should be formalized before
enrolling
for specialized instruction.
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| Revision: 2003-2004 |
Bulk, particulate and macromolecular materials from approximately
10 cubic centimeters to 0.1 nanometer can be imaged with our
microscopes.