Type of Electron
Transmission Electron Microscope
Scanning Electron Microscope
Reflection Electron Microscope
Low-Voltage Electron Microscope
The Original Form of EM that uses the
high voltage Beam of Electrons to create
Its has Resolution power up to
0.5 angstrom (50 picometres).
Most Powerful for observing
Electron Gun Produces Beam of 100 keV.
Anode and Cathode accelerate Beam.
Focusing occur by Electrostatic and
Beam strikes the sample and pass through
After emerging out it carries information
about Sample and magnify it by objective
Information can be analyzed by Screen or
Film or CCD Cameras on LCD or monitor.
TEMs offer the most powerful
magnification, potentially over one million
times or more
TEMs provide information on element and
Images are high-quality and detailed
TEMs are able to yield information of
surface features, shape, size and structure
They are easy to operate with proper
Limits of TEM
High Voltage can damage Sample.
Sample should be xtremely thin upto 100
Bio Samples are Dehydrated , chemically
fixed, embedded in polymer resin to
Staining is required to highlight in order to
achieve require image contrast.
Thinning of sample should be done upto
Scanning Electron Microscope
SEM produces the image by scanning it
with focus beam of electron.
Electrons interact with electrons in
sample and convey information in form
of signals to detectors. E.g. topography
& sample surface.
SEM can achieve resolution better than
Raster image focusing is used
When High energy Electrons strikes the
surface, it lose energy by diff.
mechanisms like heat, emission of low
energy secondary electrons and high
energy backscattered electrons.
X-ray or light emerges from sample that
carries information on it.
Its basically used for biological samples
It can scan the processes occurring on
surface and tells about topography and
Enable us to view without thinning
dehydrating fixing the sample
Can scan bulk samples upto 2-3 cm which
can not be examined by TEM.
View obtained is in 3D.
ESEM produce image of Wet, gas &
Vacuumed Samples and biological samples.
Reflection Electron Mcroscope
Its is the fixation of Transmission and
Scanning Electron Microscope.
Uses the Elastically Scattered Electrons
for focusing the electron beam into a
narrow spot which is scanned over the
sample in a raster.
Raster is the rectangular pattern of
image capture and reconstruction in
TEM Sample forming processes are involved
Highly contrasted mage is produces with
Rastering of beam occurs by focusing on
In REM Focusing action occurs before the
beam strikes the sample but in TEM focusing
action occurs after the striking
Also data is obtained in series image rather
in parallel image form.
As the Name suggests that it uses low
voltage for scanning i.e. up to 5 KeV.
Higher Contrasting focus and good quality
image are produces with good magnifying
power better then TEM.
Pinpoint image are obtained on CCD
This type can be used as
TEM, SEM, STEM.
No Staining Required
Comparison of LVEM & TEM of
Rat Heart (Specific part)
LEVM @ 5 Kev TEM @ 80 Kev
Present low voltage electron
microscopes are capable of spatial
resolutions of about 2.5 nm in TEM
2.0 nm in STEM and 3.0 nm in SEM.
Low voltage limits the maximum
thickness of samples
It is about 100–200 nm in conventional
It decreases to around 20–65
nanometers for LVEM.