IKI has a number of Electron Microscopes: Scanning Electron Microscopes, Transmission Electron Microscopes, Cryo-Transmission Electron Microscopes, Analytical-Transmission Electron Microscope.
Special modes (or accessories) comprise: EDS, EBSD, EELS, EFTEM, Phase contrast. (Read more about this below.)
Some microscopes have STEM capability.
For sample preparation: Vitrification, Critical Point Drying, Plasma Cleaning, Microtom cross-sectioning, Sputter coating, Carbon Flash deposition.
Below you find a more detailed description of Electron Microscopy, and a comprehensive list of the Instruments. (Technical details, application notes, and contact information can be found when you follow the link for a specific instrumemt.)
TEMs at IKI lab
TEM - Analytical High Resolution Transmission / Scanning Field Emission Electron Microscope (JEOL JEM 2100F)
Used to determine the composition, crystallographic structure, electronic structure, and chemical bonding of the specimen, and for mapping electric and magnetic fields.
TEM - High Resolution Conventional and Cryo Transmission / Scanning Field Emission Electron Microscope (FEI Talos F200C)
Optimized for ease of use and high throughput. Optimal settings can be stored in recipes, and recalled when needed. Excellent contrast in Low Dose Operation permits fast readout, a key factor for dynamic experiments. Especially well-suited for biomaterials (like cells) and for Cryo-TEM. 3D-characterization is made possible by the Tomography holder.
TEM - Conventional and Cryo Transmission Electron Microscope (FEI Tecnai T12)
TEM - High Resolution Transmission / Scanning Electron Microscope (JEOL JEM 2011)
SEMs at IKI lab
SEM - Scanning Electron Microscope (FEI Quanta 200)
Able to work at elevated pressure. Robust with regard to out-gasing or residual water content. Tungsten filament gun, operated at high acceleration voltages (~25 kV). Heavily used for compositional analysis through EDS and through back-scattered electron detection.
SEM - High Resolution Scanning Electron Microscope (Jeol JSM 7400F)
Field emission gun, allows for high resolution, low energy "Gentle beam" imaging (~ 1 kV). Can approach 1 nm resolution. Used for EDS mostly with smaller energies. Software option for EDS-mapping. Not suitable for "wet" samples, outgasing samples, or magnetic samples.
SEM - Extreme High Resolution Scanning Electron Microscope (FEI Verios XHR 460L)
Acchieves sub-nm resolution. Operates between 1 and 30 kV, with electron landing energies as low as 20 eV. Designed for high throughput, with automated sample loading. Advanced analytical abilities, with EBSD and STEM functionality.
Introduction to Scanning Electron Microscopy
Electron microscopes operate in vacuum, so samples must be suitable for vacuum
conditions. Scanning electron microscopes (SEM) are used to see surface
topography. Such images appear often like light microscope images, but the SEM
"topography" contrast has many contributions, and SEM and light
microscopy images of the same area can look very different. The
"beauty" of SEM-microscopy lies in the fact that it produces images
which are "in focus" even when the height differences are large. The
ability to see a sharp image of a whole fly and to zoom-in continuously until
tiny hairs in the eye of the insect are seen is fascinating. In addition,
information on the composition of the specimen can be obtained, often based on
the detection of element characteristic x-ray radiation, but also by other
For background reading: J.
I. Goldstein, Scanning Electron Microscopy and X-Ray Microanalysis. (The 3rd
edition is available in the library. However, try to get hold of the 4th
edition (2018), which is of much more practical value.)
Some things to
keep in mind:
Beam Energy: Low beam energies (more precisely: electron landing energies) provide a more realistic and
detailed image of the surface than high energies. The interaction volume grows
with the 5th power of the beam energy, so using 20 kV instead of 2
kV increases the interaction volume by a factor of 100,000.)
EDS X-ray Microanalysis: Do not get fooled when modern software supplies you
with atomic% and error bars. (The error bars are calculated from the
statistical error of the counts, and do not take care of most other errors.) The
method is NOT giving quantitative results on the fly. A key source for error is
the fact that each detector has its individual "blindness". Especially
for low energy x-rays the errors can be large. Tedious, careful experimentation
and calibration samples would be typically required for getting more
quantitative. Nevertheless, EDS (in the form of Standardless Analysis) is a useful
and convenient way to get an idea on the local composition of your sample.
EDS Mapping: This can show the spatial distribution of elements.
However, you must remove the background signal in post processing. On the
HR-SEM be sure to choose Spectral Imaging mode. (So-called Mapping
mode is completely useless, because there is no way to filter out the noise.
Don't ever use it.)
Material Contrast in
Somewhat confusing, the images obtained by the so-called "secondary
electron detector" can show a large contrast related to the average atomic
number Z of the probed volume. (Still it is true that only the yield of
back-scattered electrons is related to the average Z, while the yield of
secondary electrons does not depend on Z.) The point is simply this: Secondary
electrons are created by the incoming beam (so-called SE-1 fraction, which is
independent of Z) but also from the backscattered electrons (SE-2 and SE-3
fraction). It is possible that the SE-2 and SE-3 fraction contribute sometimes
even 90% to the total signal, and as they are created by back-scattered
electrons, this adds the Z-contrast of the back-scattered electrons to the
Charging and Image Drift: In principle it would be possible to adjust the beam
energy to a value that will keep any irradiated sample uncharged. (The number
of electrons leaving the sample equals the number of electrons entering the
sample.) In practice, this is not easy to achieve even for homogeneous samples.
We can keep in mind that this favorable point is typically between 0.5 and 4
kV, so working with low beam energies reduces charging problems. Insulating
samples are routinely coated with thin conductive layers. The sample under this
layer will still get charged, but the surface is highly conductive and this
avoids dramatic dynamic effects in the emission rate and absorption of low
energy secondary electrons. Because the sample itself still gets charged you
may see distortions or drift at steps, in particular with cross-sections.
Measuring Film Thickness at Cross-sections in the Presence of Charging.pdf